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物种起源|The Origin of Species

第五章　变异的法则|CHAPTER V　LAWS OF VARIATION

属类： 双语小说 【分类】其他读物 阅读：[5513]
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外界条件的影响——与自然选择相结合的用与废；飞翔器官和视觉器官——气候驯化——相关生长——生长的补偿和节约——假相关——重复的、残迹的及低等体制的构造易生变异——发育异常的部分易于高度变异：物种的性状比属的性状更易变异：第二性征易生变异——同属的物种以类似方式发生变异——长久亡失的性状的重现——提要

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Effects of external conditions—Use and disuse, combined with natural selection; organs of flight and of vision—Acclimatisation— Correlation of growth—Compensation and economy of growth— False correlations— Multiple, rudimentary, and lowly organised structures variable—Parts developed in an unusual manner are highly variable: specific characters more variable than generic: secondary sexual characters variable—Species of the same genus vary in an analogous manner—Reversions to long lost characters— Summary

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至此，我有时把变异说成是事出偶然，因为生物在家养状况下是如此普遍且多样，在自然状况下则不那么常见。当然，这是完全不正确的说法，但足以表明我们对于各种变异的原因一无所知。某些作者认为，产生个体差异或构造的轻微偏差，就像使孩子酷似双亲那样，是生殖系统的机能。但是，家养状况下，变异性比自然状况下更大，畸形更常发生。于是我认为，结构变异在某种程度上是生活条件的性质决定的，因为父母亲和祖先已经在这样的条件下生活了若干世代。第一章说过，生殖系统明显受生活条件变化的影响，当然需要一大串事实来证明这一点的正确性，这里从略。而后代变动的、可塑的条件，我主要归咎于父母亲的生殖系统在机能上受到了扰动。雌雄性器官似乎在形成新生命的结合发生之前就受到了影响。至于“芽变植物”的情况，芽在最早的条件下与胚珠没有本质差别，是单独受到影响的。可是，生殖系统受到扰动后，为什么这个那个部分变异更大或者更小，我们全然不知道。然而，我们时不时得到一丝丝启发，可以肯定，结构上的每次偏差，不管多么轻微，一定事出有因。

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I have hitherto sometimes spoken as if the variations—so common and multiform in organic beings under domestication, and in a lesser degree in those in a state of nature—had been due to chance. This, of course, is a wholly incorrect expression, but it serves to acknowledge plainly our ignorance of the cause of each particular variation. Some authors believe it to be as much the function of the reproductive system to produce individual differences, or very slight deviations of structure, as to make the child like its parents. But the much greater variability, as well as the greater frequency of monstrosities, under domestication or cultivation, than under nature, leads me to believe that deviations of structure are in some way due to the nature of the conditions of life, to which the parents and their more remote ancestors have been exposed during several generations. I have remarked in the first chapter—but a long catalogue of facts which cannot be here given would be necessary to show the truth of the remark—that the reproductive system is eminently susceptible to changes in the conditions of life; and to this system being functionally disturbed in the parents, I chiefly attribute the varying or plastic condition of the offspring. The male and female sexual elements seem to be affected before that union takes place which is to form a new being. In the case of “sporting” plants, the bud, which in its earliest condition does not apparently differ essentially from an ovule, is alone affected. But why, because the reproductive system is disturbed, this or that part should vary more or less, we are profoundly ignorant. Nevertheless, we can here and there dimly catch a faint ray of light, and we may feel sure that there must be some cause for each deviation of structure, however slight.

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气候、食物等的改变，发生了多大直接作用，令人莫衷一是。我的印象是，在动物方面作用极微，而植物方面也许影响多一点。至少可以稳妥地断言，这种作用不能产生如我们在自然界的各种生物间所看到的构造的许多复杂的相互适应。一些微小的影响可以归结于气候、食物等等。例如福布斯（E. Forbes）断言，生长在最南方的贝类，如果是浅水的，颜色要比北方的或深水的同种贝类来得鲜明。古尔德（Gould）先生相信，同种的鸟，生活在明朗大气中的，颜色要比生活在海边或海岛上的来得鲜艳。昆虫也是如此，沃拉斯顿相信，海边生活会影响其颜色。摩坤-丹顿（Moquin-Tandon）曾列出一张植物表，所举的植物生长在近海岸处时，在某种程度上叶多肉质，虽然在别处并不如此。另外尚能举出若干类似例子。

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How much direct effect difference of climate, food, etc., produces on any being is extremely doubtful. My impression is, that the effect is extremely small in the case of animals, but perhaps rather more in that of plants. We may, at least, safely conclude that such influences cannot have produced the many striking and complex co-adaptations of structure between one organic being and another, which we see everywhere throughout nature. Some little influence may be attributed to climate, food, etc.: thus, E. Forbes speaks confidently that shells at their southern limit, and when living in shallow water, are more brightly coloured than those of the same species further north or from greater depths. Gould believes that birds of the same species are more brightly coloured under a clear atmosphere, than when living on islands or near the coast. So with insects, Wollaston is convinced that residence near the sea affects their colours. Moquin-Tandon gives a list of plants which when growing near the sea-shore have their leaves in some degree fleshy, though not elsewhere fleshy. Several other such cases could be given.

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一个物种分布到其他物种的生长区，其变种常常稍微获得该物种的某些性状，这一点符合我们关于各种物种只不过是清晰标记的永久变种的观点。比如囿于热带浅海的贝类，一般比深海冷水贝类的外壳更加艳丽。内陆鸟类比海岛鸟类颜色更加鲜艳，这是古尔德先生的观点。收藏者都知道，囿于沿海的昆虫，外壳往往是古铜色或者鲜艳色的。囿于海滨的植物容易生长肉质的叶子。相信每一个物种都是神创的人必定会说，这个贝类为了暖和的海水而天生鲜艳的贝壳，而另一种贝类分布到暖水浅海时就因变异而变得鲜艳了。

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The fact of varieties of one species, when they range into the zone of habitation of other species, often acquiring in a very slight degree some of the characters of such species, accords with our view that species of all kinds are only well-marked and permanent varieties. Thus the species of shells which are confined to tropical and shallow seas are generally brighter-coloured than those confined to cold and deeper seas. The birds which are confined to continents are, according to Mr. Gould, brighter-coloured than those of islands. The insect-species confined to sea-coasts, as every collector knows, are often brassy or lurid. Plants which live exclusively on the sea-side are very apt to have fleshy leaves. He who believes in the creation of each species, will have to say that this shell, for instance, was created with bright colours for a warm sea; but that this other shell became bright-coloured by variation when it ranged into warmer or shallower waters.

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当变异对生物有极微小的用处时，就无法说出这一变异有多少应当归因于自然选择的累积作用，有多少应当归因于生活条件作用。例如，皮货商都很熟悉，同种动物生活的气候越严寒，毛皮就越厚越好；但谁能说出差异有多少是由于毛皮最温暖的个体在许多世代中得到惠及而被保存，有多少是由于严寒气候的直接作用呢？因为气候似乎对于家畜的毛皮是有某种直接作用的。

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When a variation is of the slightest use to a being, we cannot tell how much of it to attribute to the accumulative action of natural selection, and how much to the conditions of life. Thus, it is well known to furriers that animals of the same species have thicker and better fur the more severe the climate is under which they have lived; but who can tell how much of this difference may be due to the warmest-clad individuals having been favoured and preserved during many generations, and how much to the direct action of the severe climate? for it would appear that climate has some direct action on the hair of our domestic quadrupeds.

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同一物种在分明不同的外界条件下，产生了相同的变种，而在相同的外界条件下，却产生了不相似的变种，这样的事例不胜枚举，表明生活条件的作用想必是何等间接。还有，有些物种虽然生活在极相反的气候下，仍能保持纯粹，完全不变，这样的事例不计其数，学者人人都熟悉的。这种情况使我不重视周围条件的直接作用。上面提及，间接地，周围条件似乎能大大影响生殖系统，从而引起变异性。然后，自然选择将有益的变异统统积累起来，不管多么轻微，直到明显发展，为我们所察觉。

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Instances could be given of the same variety being produced under conditions of life as different as can well be conceived; and, on the other hand, of different varieties being produced from the same species under the same conditions. Such facts show how indirectly the conditions of life must act. Again, innumerable instances are known to every naturalist of species keeping true, or not varying at all, although living under the most opposite climates. Such considerations as these incline me to lay very little weight on the direct action of the conditions of life. Indirectly, as already remarked, they seem to play an important part in affecting the reproductive system, and in thus inducing variability; and natural selection will then accumulate all profitable variations, however slight, until they become plainly developed and appreciable by us.

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用和废的作用。——根据第一章所述，家养动物有些器官因使用而加强和增大，有些器官因不使用而缩小，我想这是无可怀疑的，而且这种变化是遗传的。在不受拘束的自然状况下，由于不知道祖代的类型，所以没有比较的标准来判别长久连续使用和不使用的效果；但是许多动物所具有的构造，是能够按不使用的效果而解释的。欧文教授说，自然界没有比鸟不能飞更为异常的了，然而若干鸟类却是这样的。南美洲的大头鸭（logger-headed duck）只能在水面上扑腾翅膀，翅膀几乎和家养的艾尔斯伯里鸭（Aylesbury duck）一样。地上觅食的大型鸟，除避险以外很少飞翔，所以我认为现今或不久之前栖息在无猛兽海岛上的几种鸟几乎没有翅膀，是不使用的缘故。鸵鸟的确是栖息在大陆上的，它暴露在不能靠飞翔来逃脱的危险下，但能够像小型四足兽那样踢敌自卫。可以想象，鸵鸟一属的祖先，习性原是和大雁相像的，但自然选择在连续的世代里增加了其身体的大小重量，就更多地用腿，而更少地用翅膀，终于变得不能飞翔。

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Effects of Use and Disuse.—From the facts alluded to in the first chapter, I think there can be little doubt that use in our domestic animals strengthens and enlarges certain parts, and disuse diminishes them; and that such modifications are inherited. Under free nature, we can have no standard of comparison, by which to judge of the effects of long-continued use or disuse, for we know not the parent-forms; but many animals have structures which can be explained by the effects of disuse. As Professor Owen has remarked, there is no greater anomaly in nature than a bird that cannot fly; yet there are several in this state. The logger-headed duck of South America can only flap along the surface of the water, and has its wings in nearly the same condition as the domestic Aylesbury duck. As the larger ground-feeding birds seldom take flight except to escape danger, I believe that the nearly wingless condition of several birds, which now inhabit or have lately inhabited several oceanic islands, tenanted by no beast of prey, has been caused by disuse. The ostrich indeed inhabits continents and is exposed to danger from which it cannot escape by flight, but by kicking it can defend itself from enemies, as well as any of the smaller quadrupeds. We may imagine that the early progenitor of the ostrich had habits like those of a bustard, and that as natural selection increased in successive generations the size and weight of its body, its legs were used more, and its wings less, until they became incapable of flight.

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柯比（Kirby）说过（我也曾看到过同样的事实），许多吃粪的雄性甲虫的前趾节，即前足常常会断掉；他检查了所采集的十七个标本，没有一个留有一点痕迹。阿佩勒蜣螂（Onites apelles）前足跗节的亡失司空见惯，所以常描述为不具有跗节。某些其他属虽具有跗节，但只是一种残迹的状态而已。埃及人的圣甲虫（Ateuchus）跗节完全缺如。没有足够的证据可以认为肢体损伤能遗传；我认为，圣甲虫全然没有前足跗节，某些其他属仅仅留有跗节的残迹，最妥当的解释是祖先长久持续不使用的结果；因为许多吃粪的甲虫一般都失去了跗节，这一定发生在生命早期；所以，此种昆虫无法大事使用跗节。

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Kirby has remarked (and I have observed the same fact) that the anterior tarsi, or feet, of many male dung-feeding beetles are very often broken off; he examined seventeen specimens in his own collection, and not one had even a relic left. In the Onites apelles the tarsi are so habitually lost, that the insect has been described as not having them. In some other genera they are present, but in a rudimentary condition. In the Ateuchus or sacred beetle of the Egyptians, they are totally deficient. There is not sufficient evidence to induce us to believe that mutilations are ever inherited; and I should prefer explaining the entire absence of the anterior tarsi in Ateuchus, and their rudimentary condition in some other genera, by the long-continued effects of disuse in their progenitors; for as the tarsi are almost always lost in many dung-feeding beetles, they must be lost early in life, and therefore cannot be much used by these insects.

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在某些个案里，很容易把全部或主要由自然选择所引起的构造变异归咎于不使用。沃拉斯顿先生发现了一件引人注目的事实，就是栖息在马德拉的550种甲虫中，有200种甲虫的翅膀不完全而不能飞翔；二十九个土著的属中，不下二十三个属的所有物种都是这样的情况！还有，世界上有许多地方的甲虫常常被风刮到海中溺死，而马德拉的甲虫据沃拉斯顿的观察，隐蔽得很好，直到风和日丽方才出来；无翅甲虫的比例数，在没有遮拦的德塞塔群岛（Desertas）比在马德拉更大。特别奇异的是，沃拉斯顿特别重视一个事实，生活习性需要经常使用翅膀的某些大群甲虫，其他各地非常多，但这里却几乎绝迹——凡此种种，让我相信，这么多的马德拉甲虫之所以没有翅膀，主因是自然选择的作用，也许配合了不使用。因为在成千上万连续的世代中，有些甲虫个体要么翅膀发育得稍不完全，要么习性怠惰，飞翔最少，不会被风吹到海里去，因而获得最好的生存机会；反之，最喜欢飞翔的甲虫个体最常被风吹到海里去，因而遭到毁灭。

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In some cases we might easily put down to disuse modifications of structure which are wholly, or mainly, due to natural selection. Mr. Wollaston has discovered the remarkable fact that 200 beetles, out of the 550 species inhabiting Madeira, are so far deficient in wings that they cannot fly; and that of the twenty-nine endemic genera, no less than twenty-three genera have all their species in this condition! Several facts, namely, that beetles in many parts of the world are very frequently blown to sea and perish; that the beetles in Madeira, as observed by Mr. Wollaston, lie much concealed, until the wind lulls and the sun shines; that the proportion of wingless beetles is larger on the exposed Dezertas than in Madeira itself; and especially the extraordinary fact, so strongly insisted on by Mr. Wollaston, of the almost entire absence of certain large groups of beetles, elsewhere excessively numerous, and which groups have habits of life almost necessitating frequent flight;—these several considerations have made me believe that the wingless condition of so many Madeira beetles is mainly due to the action of natural selection, but combined probably with disuse. For during thousands of successive generations each individual beetle which flew least, either from its wings having been ever so little less perfectly developed or from indolent habit, will have had the best chance of surviving from not being blown out to sea; and, on the other hand, those beetles which most readily took to flight will oftenest have been blown to sea and thus have been destroyed.

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马德拉也有不在地面觅食的昆虫，如某些在花朵中觅食的鞘翅类和鳞翅类，必须经常使用翅膀以获取食物，据沃拉斯顿先生猜测，这些昆虫的翅膀不但一点也没有缩小，甚至会更加增大。这完全符合自然选择的作用。当新的昆虫最初到达此岛时，增大或者缩小翅膀的自然选择的倾向，将取决于战风胜利而保存下来的个体多，还是放弃这种企图，少飞、不飞而保存下来的个体多。譬如船在近海失事，对于船员来说，善于游泳的游得越远越好，不善于游泳的，攀住破船倒好些。

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The insects in Madeira which are not ground-feeders, and which, as the flower-feeding coleoptera and lepidoptera, must habitually use their wings to gain their subsistence, have, as Mr. Wollaston suspects, their wings not at all reduced, but even enlarged. This is quite compatible with the action of natural selection. For when a new insect first arrived on the island, the tendency of natural selection to enlarge or to reduce the wings, would depend on whether a greater number of individuals were saved by successfully battling with the winds, or by giving up the attempt and rarely or never flying. As with mariners shipwrecked near a coast, it would have been better for the good swimmers if they had been able to swim still further, whereas it would have been better for the bad swimmers if they had not been able to swim at all and had stuck to the wreck.

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鼹鼠和某些穴居的啮齿类动物，眼睛大小如残迹，某些个案的眼睛被皮和毛所遮盖。眼睛的这种状态大概是由于不使用而渐渐缩小的缘故，不过这里恐怕也辅以自然选择。南美洲一种穴居的啮齿动物，叫作吐科吐科（tuco-tuco），拉丁文Ctenomys，深入地下的习性甚至有过于鼹鼠；一位常捉此动物的西班牙人告诉我说，其眼睛多半是瞎的。我养过一只活的，眼睛的确是这种情形，解剖后才知道原因，瞬膜发炎。眼睛常常发炎对于任何动物必定是有害的，而眼睛对穴居习性的动物肯定不是必要的，所以眼睛缩小，上下眼睑粘连，上面生毛，可能是有利的；倘使有利，自然选择就会不断辅助不使用的效果。

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The eyes of moles and of some burrowing rodents are rudimentary in size, and in some cases are quite covered up by skin and fur. This state of the eyes is probably due to gradual reduction from disuse, but aided perhaps by natural selection. In South America, a burrowing rodent, the tuco-tuco, or Ctenomys, is even more subterranean in its habits than the mole; and I was assured by a Spaniard, who had often caught them, that they were frequently blind; one which I kept alive was certainly in this condition, the cause, as appeared on dissection, having been inflammation of the nictitating membrane. As frequent inflammation of the eyes must be injurious to any animal, and as eyes are certainly not indispensable to animals with subterranean habits, a reduction in their size with the adhesion of the eyelids and growth of fur over them, might in such case be an advantage; and if so, natural selection would constantly aid the effects of disuse.

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众所熟知，奥地利施蒂里亚（Styria）及美国肯塔基州（Kentucky）的洞穴里，栖息有几种属于极其不同纲的盲目动物。某些蟹虽然已经没有眼睛，眼柄却依然存在；望远镜的透镜已经丢了，而镜架还依然存在。对于生活在黑暗中的动物来说，眼睛虽然没有用处，很难想象会有什么害处，所以其亡失归因于不使用。有一种盲目动物，叫作洞鼠（cave-rat），两只眼睛硕大。西利曼（Silliman）教授认为，在光线下生活若干天后，它恢复了微弱的视力。就像马德拉岛一样，某些昆虫的翅膀扩大了，某些昆虫的翅膀缩小了，原因是自然选择，辅助以用和废；洞鼠的情况是，自然选择似乎与失去光线斗争过，扩大了眼睛的尺寸；而对于洞中所有其他动物而言，似乎唯有不使用大显身手了。

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It is well known that several animals, belonging to the most different classes, which inhabit the caves of Styria and of Kentucky, are blind. In some of the crabs the foot-stalk for the eye remains, though the eye is gone; the stand for the telescope is there, though the telescope with its glasses has been lost. As it is difficult to imagine that eyes, though useless, could be in any way injurious to animals living in darkness, I attribute their loss wholly to disuse. In one of the blind animals, namely, the cave-rat, the eyes are of immense size; and Professor Silliman thought that it regained, after living some days in the light, some slight power of vision. In the same manner as in Madeira the wings of some of the insects have been enlarged, and the wings of others have been reduced by natural selection aided by use and disuse, so in the case of the cave-rat natural selection seems to have struggled with the loss of light and to have increased the size of the eyes; whereas with all the other inhabitants of the caves, disuse by itself seems to have done its work.

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很难想象，生活条件还有比几乎相似气候下的石灰岩大洞更为相似的了；所以按照盲目动物系为美洲和欧洲的岩洞分别创造出来的旧观点，可以预料到它们的体制和亲缘是极其相似的。可希厄特（Schi?dte）等人指出，情况并非如此；两大陆的岩洞昆虫，预料也不比欧洲和北美洲的动物之间的一般类似性更密切相关。依我看，必须假定美洲动物具有正常的视力，它们逐代慢慢地从外界移入肯塔基洞穴的越来越深的处所，就像欧洲动物移入欧洲的洞穴里那样。我们有这种习性渐变的某种证据；希厄特说过：“预备从光明转入黑暗的动物，与普通类型相距并不远。构造适于微光的类型继之而起，最后是适于全黑暗的那些类型。”动物经过无数世代，达到最深的深处时，眼睛因不使用而差不多完全灭迹了，而自然选择常常会引起别的变化，如触角或触须的增长，作为盲目的补偿。尽管有这种变异，我们还能看出美洲的洞穴动物与美洲大陆别种动物的亲缘关系，欧洲的洞穴动物与欧洲大陆动物的亲缘关系。我听达纳（Dana）教授说过，美洲的某些洞穴动物确系如此，而欧洲的某些洞穴昆虫与其周围地方的昆虫极其密切相似。如果按独立创造的普通观点来看，对于盲目的洞穴动物与该两大陆其他动物之间的亲缘关系，就很难给予合理的解释。新旧两个世界的若干洞穴动物的亲缘密切关联，可从众所周知的这两个世界的大多数其他生物间的关系料想到。有些穴居动物十分古怪，如阿加西斯（Agassiz）说过的洞鲈（Amblyopsis），又如欧洲的爬行动物洞螈（Proteus），这没有什么值得大惊小怪的，我所惊奇的只是古生物的残余没有保存得更多，因为住在这种黑暗处所的动物，竞争也许并不激烈。

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It is difficult to imagine conditions of life more similar than deep limestone caverns under a nearly similar climate; so that on the common view of the blind animals having been separately created for the American and European caverns, close similarity in their organisation and affinities might have been expected; but, as Schi?dte and others have remarked, this is not the case, and the cave-insects of the two continents are not more closely allied than might have been anticipated from the general resemblance of the other inhabitants of North America and Europe. On my view we must suppose that American animals, having ordinary powers of vision, slowly migrated by successive generations from the outer world into the deeper and deeper recesses of the Kentucky caves, as did European animals into the caves of Europe. We have some evidence of this gradation of habit; for, as Schi?dte remarks, “animals not far remote from ordinary forms, prepare the transition from light to darkness. Next follow those that are constructed for twilight; and, last of all, those destined for total darkness.” By the time that an animal had reached, after numberless generations, the deepest recesses, disuse will on this view have more or less perfectly obliterated its eyes, and natural selection will often have effected other changes, such as an increase in the length of the antennae or palpi, as a compensation for blindness. Notwithstanding such modifications, we might expect still to see in the cave-animals of America, affinities to the other inhabitants of that continent, and in those of Europe, to the inhabitants of the European continent. And this is the case with some of the American cave-animals, as I hear from Professor Dana; and some of the European cave-insects are very closely allied to those of the surrounding country. It would be most difficult to give any rational explanation of the affinities of the blind cave-animals to the other inhabitants of the two continents on the ordinary view of their independent creation. That several of the inhabitants of the caves of the Old and New Worlds should be closely related, we might expect from the well-known relationship of most of their other productions. Far from feeling any surprise that some of the cave-animals should be very anomalous, as Agassiz has remarked in regard to the blind fish, the Amblyopsis, and as is the case with the blind Proteus with reference to the reptiles of Europe, I am only surprised that more wrecks of ancient life have not been preserved, owing to the less severe competition to which the inhabitants of these dark abodes will probably have been exposed.

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气候驯化。——植物的习性是遗传的，如开花期、种子发芽时所需要的雨量、休眠的时间等等，因此我要略谈一下气候驯化。同属不同种的植物栖息在热地和寒地原是极其普通的，我认为同属的一切物种确是由单一的亲种传下来的，如果说得对，那么气候驯化必定在传承的长期过程中轻易实现。众所周知，每一物种都适应其本土气候：从寒带甚至从温带来的物种不能忍受热带气候，反过来也是一样。还有许多多汁植物不能忍受潮湿气候。但是，一个物种对于生境气候的适应程度常常被高估。我们往往无法预知一种引进植物能否忍受我们的气候，而从温暖地区引进在这里健康生长的动植物屈指可数，就是明证。有理由相信，在自然状况下，物种在分布上的限制因素，生物竞争高于等于生境气候的适应。但是不管这种适应是否普遍很贴切，有证据可以证明，少数植物好歹变得自然习惯于不同的气温了；这就是说，它们驯化了：胡克博士从喜马拉雅山上的不同高度，采集了松树和杜鹃花属的种子，栽培在英国，发现其具有不同的抗寒力。思韦茨（Thwaites）先生告诉我说，他在锡兰看到过同样事实；沃森先生曾把欧洲种的植物从亚速尔群岛（Azores）带回英国做过类似的观察。关于动物，也有若干确实的事例可以引证，有历史记载以来，物种大大地扩展分布范围，从较暖的纬度扩展到较冷的纬度，反之亦然；但是我们无法肯定，这些动物是否严格适应其本土的气候，虽然在一般情形下我们假定是这样的；我们也不知道，后来是否对于新家乡变得驯化。

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acclimatisation.—Habit is hereditary with plants, as in the period of flowering, in the amount of rain requisite for seeds to germinate, in the time of sleep, etc., and this leads me to say a few words on acclimatisation. As it is extremely common for species of the same genus to inhabit very hot and very cold countries, and as I believe that all the species of the same genus have descended from a single parent, if this view be correct, acclimatisation must be readily effected during long-continued descent. It is notorious that each species is adapted to the climate of its own home: species from an arctic or even from a temperate region cannot endure a tropical climate, or conversely. So again, many succulent plants cannot endure a damp climate. But the degree of adaptation of species to the climates under which they live is often overrated. We may infer this from our frequent inability to predict whether or not an imported plant will endure our climate, and from the number of plants and animals brought from warmer countries which here enjoy good health. We have reason to believe that species in a state of nature are limited in their ranges by the competition of other organic beings quite as much as, or more than, by adaptation to particular climates. But whether or not the adaptation be generally very close, we have evidence, in the case of some few plants, of their becoming, to a certain extent, naturally habituated to different temperatures, or becoming acclimatised: thus the pines and rhododendrons, raised from seed collected by Dr. Hooker from trees growing at different heights on the Himalaya, were found in this country to possess different constitutional powers of resisting cold. Mr. Thwaites informs me that he has observed similar facts in Ceylon, and analogous observations have been made by Mr. H. C. Watson on European species of plants brought from the Azores to England. In regard to animals, several authentic cases could be given of species within historical times having largely extended their range from warmer to cooler latitudes, and conversely; but we do not positively know that these animals were strictly adapted to their native climate, but in all ordinary cases we assume such to be the case; nor do we know that they have subsequently become acclimatised to their new homes.

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我认为，家养动物最初是由未开化人选择出来的，理由是有用，同时在幽禁状态下容易生育，而不是因为后来发现它们能够输送到遥远的地方去。我想，家养动物共同的能力十分出色，不仅能够抵御千差万别的气候，而且在那种气候下完全能生育（这是更为严峻的考验）。据此可以论证，现今生活在自然状况下的动物，大多数容易引入并能够抵御千差万别的气候。然而，我们千万不要把上述论点牵强附会，因为家养动物可能起源于若干个野生祖先。例如，热带狼和寒带狼、野狗的血统恐怕混合在家犬品种里面。大鼠（rat）和家鼠（mouse）不能看作是家养动物，却被人带到世界的许多地方去，现在分布之广，远超任何其他啮齿动物；自由生活于北半球法罗群岛（Faroe）和南半球福克兰群岛（Falklands）的寒冷气候下，还生活在赤日炎炎的许多热带岛屿上。因此，对于特殊气候的适应，可以看作是大多数动物所共有的性质，容易移植于体质中内在的广泛柔性里去。根据这种观点，人类自己和家养动物对于千差万别气候的忍受能力，以及古代的大象和犀牛能忍受冰河期的气候，而它们的现存种却具有热带亚热带的习性，这些都不应看作异常的事情，而应看作是很普通的体质柔性在特殊环境下起作用的事例。

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As I believe that our domestic animals were originally chosen by uncivilised man because they were useful and bred readily under confinement, and not because they were subsequently found capable of far-extended transportation, I think the common and extraordinary capacity in our domestic animals of not only withstanding the most different climates but of being perfectly fertile (a far severer test) under them, may be used as an argument that a large proportion of other animals, now in a state of nature, could easily be brought to bear widely different climates. We must not, however, push the foregoing argument too far, on account of the probable origin of some of our domestic animals from several wild stocks: the blood, for instance, of a tropical and arctic wolf or wild dog may perhaps be mingled in our domestic breeds. The rat and mouse cannot be considered as domestic animals, but they have been transported by man to many parts of the world, and now have a far wider range than any other rodent, living free under the cold climate of Faroe in the north and of the Falklands in the south, and on many islands in the torrid zones. Hence I am inclined to look at adaptation to any special climate as a quality readily grafted on an innate wide flexibility of constitution, which is common to most animals. On this view, the capacity of enduring the most different climates by man himself and by his domestic animals, and such facts as that former species of the elephant and rhinoceros were capable of enduring a glacial climate, whereas the living species are now all tropical or sub-tropical in their habits, ought not to be looked at as anomalies, but merely as examples of a very common flexibility of constitution, brought, under peculiar circumstances, into play.

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物种对于特殊气候的驯化，有多少是单纯出于习性，有多少是出于具有不同内在体质的变种的自然选择，有多少是兼而有之，这是一个难解的问题。不管是类推类比，还是农业著作甚至古代的中国百科全书的谆谆忠告，都说把动物从此地运到彼地必须十分小心，所以我必须相信习性习惯是有一些影响的。因为人类不大可能成功选择那么多的品种和亚品种，都具有特别适于他们地区的体质。我想，造成这种结果的一定是习性。另一方面，自然选择必然始终倾向于保存生来就具有最适于居住地的体质的个体，这一点毋庸置疑。论述多种栽培植物的论文里说，某些变种比其他变种更善于抵御某种气候。美国出版的果树著作明确说，某些变种惯常推荐给北方，某些变种推荐给南方；由于这些变种大多起源于近代，其体质差异不能归因于习性。洋姜（Jerusalem artichoke）从来不用种子繁殖，因而也没有产生过新变种，甚至有人提出这个例子，证明气候驯化是无法实现的，因为它一如既往地娇嫩！又如，菜豆（kidney-bean）的例子也常常因相同目的而被引证，并且更为有力；但是除非有人持续二十代播种菜豆过早，使之极大部分被霜所毁，之后从少数的生存者中采集种子，并且注意防止偶然杂交，然后同样小心地再从这些幼苗采集种子进行播种，就不能说这个试验是做过了。也不能假定菜豆实生苗的体质从来不产生差异，因为有一个报告说，某些实生苗确比其他实生苗具有更大的抗寒力。

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How much of the acclimatisation of species to any peculiar climate is due to mere habit, and how much to the natural selection of varieties having different innate constitutions, and how much to both means combined, is a very obscure question. That habit or custom has some influence I must believe, both from analogy, and from the incessant advice given in agricultural works, even in the ancient Encyclopaedias of China, to be very cautious in transposing animals from one district to another; for it is not likely that man should have succeeded in selecting so many breeds and sub-breeds with constitutions specially fitted for their own districts: the result must, I think, be due to habit. On the other hand, I can see no reason to doubt that natural selection will continually tend to preserve those individuals which are born with constitutions best adapted to their native countries. In treatises on many kinds of cultivated plants, certain varieties are said to withstand certain climates better than others: this is very strikingly shown in works on fruit trees published in the United States, in which certain varieties are habitually recommended for the northern, and others for the southern States; and as most of these varieties are of recent origin, they cannot owe their constitutional differences to habit. The case of the Jerusalem artichoke, which is never propagated by seed, and of which consequently new varieties have not been produced, has even been advanced—for it is now as tender as ever it was—as proving that acclimatisation cannot be effected! The case, also, of the kidney- bean has been often cited for a similar purpose, and with much greater weight; but until some one will sow, during a score of generations, his kidney-beans so early that a very large proportion are destroyed by frost, and then collect seed from the few survivors, with care to prevent accidental crosses, and then again get seed from these seedlings, with the same precautions, the experiment cannot be said to have been even tried. Nor let it be supposed that no differences in the constitution of seedling kidney-beans ever appear, for an account has been published how much more hardy some seedlings appeared to be than others.

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总之，我想可以得出结论，习性、用废在某些个案中对于各种器官体质和构造的变异是有重要作用的，但用废效果大都往往和内在变异的自然选择相结合，有时后者还会支配这一效果。

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On the whole, I think we may conclude that habit, use, and disuse, have, in some cases, played a considerable part in the modification of the constitution, and of the structure of various organs; but that the effects of use and disuse have often been largely combined with, and sometimes overmastered by, the natural selection of innate differences.

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相关生长。——这个术语的意思是，整个体制在生长发育中紧密结合在一起，任何一部分发生些微的变异，而被自然选择所累积时，其他部分也要变异。这是一个至关重要的主题，对此所知甚少。最明显不过的个例，就是唯有对于幼龄动物或幼虫有益的累积变异，将影响成年动物的构造，这一结论可以有把握。影响早期胚胎的畸形，同样严重地影响成年动物的体制。同源的、在胚胎早期相似的身体若干部分，似乎倾向于按照关联方式进行变异：我们看到身体的右侧和左侧，按照同样方式进行变异；前腿和后腿，甚至颚和四肢一起变异，因为人们认为下颚和四肢是同源的。我不怀疑，这些倾向好歹完全受着自然选择的支配。例如，只在一侧生角的一群雄鹿一度存在过，如果这一点对于该品种曾经有过任何大的用处，大概自然选择就会使它成为永久的了。

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Correlation of Growth.—I mean by this expression that the whole organisation is so tied together during its growth and development, that when slight variations in any one part occur, and are accumulated through natural selection, other parts become modified. This is a very important subject, most imperfectly understood. The most obvious case is, that modifications accumulated solely for the good of the young or larva, will, it may safely be concluded, affect the structure of the adult; in the same manner as any malconformation affecting the early embryo, seriously affects the whole organisation of the adult. The several parts of the body which are homologous, and which, at an early embryonic period, are alike, seem liable to vary in an allied manner: we see this in the right and left sides of the body varying in the same manner; in the front and hind legs, and even in the jaws and limbs, varying together, for the lower jaw is believed to be homologous with the limbs. These tendencies, I do not doubt, may be mastered more or less completely by natural selection: thus a family of stags once existed with an antler only on one side; and if this had been of any great use to the breed it might probably have been rendered permanent by natural selection.

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某些作者说过，同源的部分有合生的倾向；在畸形植物里常常看到这情形；正常构造里同源器官的结合是再普通不过的，比如花瓣结合成管状。坚硬的部分似乎能影响相连接的柔软部分的形态；某些作者认为，鸟类骨盘形状的多样化使肾的形状发生显著的多样化。另外一些人相信，人类母亲的骨盘形状由于压力会影响胎儿头部的形状。施莱格尔（Schlegel）说，蛇类身体的形状和吞食的状态决定若干最重要的内脏的位置。

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Homologous parts, as has been remarked by some authors, tend to cohere; this is often seen in monstrous plants; and nothing is more common than the union of homologous parts in normal structures, as the union of the petals of the corolla into a tube. Hard parts seem to affect the form of adjoining soft parts; it is believed by some authors that the diversity in the shape of the pelvis in birds causes the remarkable diversity in the shape of their kidneys. Others believe that the shape of the pelvis in the human mother influences by pressure the shape of the head of the child. In snakes, according to Schlegel, the shape of the body and the manner of swallowing determine the position of several of the most important viscera.

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这种关联结合的性质，往往令人费解。小圣提雷尔先生曾强调指出，畸形有些频繁共存，另外一些则很少共存，令人莫名其妙。对于猫，蓝眼睛与耳聋的关系，黄黑色相间与雌猫的关系；对于鸽，有羽毛的脚与外趾间蹼皮的关系，雏鸽绒毛的多寡与成年鸽羽毛颜色的关系；还有，土耳其裸狗的毛与牙的关系；虽然同源也许在这里起着作用，难道还有比这些关系更为奇特的吗？关于上述相关作用的最后一例，我想并非偶然的是，随便选出哺乳动物中表皮最异常的二目，即鲸类和贫齿类（犰狳及穿山甲等），同样全部都有最异常的牙齿。

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The nature of the bond of correlation is very frequently quite obscure. M. Is. Geoffroy St. Hilaire has forcibly remarked, that certain malconformations very frequently, and that others rarely coexist, without our being able to assign any reason. What can be more singular than the relation between blue eyes and deafness in cats, and the tortoise-shell colour with the female sex; the feathered feet and skin between the outer toes in pigeons, and the presence of more or less down on the young birds when first hatched, with the future colour of their plumage; or, again, the relation between the hair and teeth in the naked Turkish dog, though here probably homology comes into play? With respect to this latter case of correlation, I think it can hardly be accidental, that if we pick out the two orders of mammalia which are most abnormal in their dermal coverings, viz. Cetacea (whales) and Edentata (armadilloes, scaly ant-eaters, etc.), that these are likewise the most abnormal in their teeth.

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据我所知，要表明和使用无关因而和自然选择无关的相关法则在重要构造变异上的重要性，没有任何个案比某些菊科（Compositous）和伞形科（Umbelliferous）植物的内花和外花的差异更为适宜的了。众所周知，雏菊等的中花和边花是有差异的，并且往往伴随着花的部分败育。但某些菊科植物的种子在形状和刻纹上也有差异；连子房本身，包括附属器官，都有差异，卡西尼说过的。有些作者把这些差异归因于压力，而且某些菊科边花内种子形状与这一想法相符；但是胡克博士告诉我，伞形科花冠的情况，其内花外花差异大的，往往决不是花序最密的那些物种。可以设想，外花花瓣的发育靠着从其他花朵器官吸收养料，就造成了器官的发育不全；但在某些菊科植物里，花冠并无不同，而内外花的种子却有差异。这些差异可能与流向中心花和外围花的养料流不同有关：至少我们知道，关于不整齐花，那些最接近花轴的最易变成反常整齐花（peloria），也就是整齐花。关于这一点，我再补充一个例子，是相关作用的惊人例子，我最近发现许多天竺葵属（Pelargonium）植物里，花束的中央花的上方二瓣常常失去深色的斑点；如果发生这情形，其附着的蜜腺即大为退化。如果上方的二瓣中只有一瓣失去颜色，蜜腺只是大大地缩短了。

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I know of no case better adapted to show the importance of the laws of correlation in modifying important structures, independently of utility and, therefore, of natural selection, than that of the difference between the outer and inner flowers in some Compositous and Umbelliferous plants. Every one knows the difference in the ray and central florets of, for instance, the daisy, and this difference is often accompanied with the abortion of parts of the flower. But, in some Compositous plants, the seeds also differ in shape and sculpture; and even the ovary itself, with its accessory parts, differs, as has been described by Cassini. These differences have been attributed by some authors to pressure, and the shape of the seeds in the ray-florets in some Compositae countenances this idea; but, in the case of the corolla of the Umbelliferae, it is by no means, as Dr. Hooker informs me, in species with the densest heads that the inner and outer flowers most frequently differ. It might have been thought that the development of the ray-petals by drawing nourishment from certain other parts of the flower had caused their abortion; but in some Compositae there is a difference in the seeds of the outer and inner florets without any difference in the corolla. Possibly, these several differences may be connected with some difference in the flow of nutriment towards the central and external flowers: we know, at least, that in irregular flowers, those nearest to the axis are oftenest subject to peloria, and become regular. I may add, as an instance of this, and of a striking case of correlation, that I have recently observed in some garden pelargoniums, that the central flower of the truss often loses the patches of darker colour in the two upper petals; and that when this occurs, the adherent nectary is quite aborted; when the colour is absent from only one of the two upper petals, the nectary is only much shortened.

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关于花冠中花序中心花和外花的差别，斯普伦格尔说，边花的用处在于引诱昆虫，昆虫的媒介对于这两目植物的受精是高度有利的，我对这一意见并不觉得牵强附会，尽管乍看好像没道理；如果有利，则自然选择可能已经起作用了。但是，关于种子内外构造上的差别，不一定和花的差异相关，因而似乎不可能对植物有什么利益：而在伞形科植物里，此等差异具有明显的重要性——陶希（Tausch）说，外围花的种子的胚乳有时候是平腹的，中心花的种子胚乳却是中空的——所以老德康多尔用类比差别对此目植物进行主要分类。因此，分类学者们高度重视的构造变异，也许全部由于不明相关生长法则所致，据我们所能判断的，这对于物种并没有丝毫的用处。

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With respect to the difference in the corolla of the central and exterior flowers of a head or umbel, I do not feel at all sure that C. C. Sprengel’s idea that the ray-florets serve to attract insects, whose agency is highly advantageous in the fertilisation of plants of these two orders, is so far-fetched, as it may at first appear: and if it be advantageous, natural selection may have come into play. But in regard to the differences both in the internal and external structure of the seeds, which are not always correlated with any differences in the flowers, it seems impossible that they can be in any way advantageous to the plant: yet in the Umbelliferae these differences are of such apparent importance—the seeds being in some cases, according to Tausch, orthospermous in the exterior flowers and coelospermous in the central flowers,—that the elder De Candolle founded his main divisions of the order on analogous differences. Hence we see that modifications of structure, viewed by systematists as of high value, may be wholly due to unknown laws of correlated growth, and without being, as far as we can see, of the slightest service to the species.

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物种的整个群所共有的、并且确实单由遗传而来的构造，往往错误地归因于相关生长；一个古代的祖先通过自然选择，可能已获得了某一种构造上的变异，而且经过数千代以后，又获得了另一种与上述变异无关的变异；这两种变异如果遗传给习性多样化的全体后代，那么自然会使我们想到它们在某种方式上一定是相关的。所以，我不怀疑还有些其他明显的相关情况在整个的目里出现，显然由自然选择的单独作用所致。例如，德康多尔说，有翅的种子从来不见于不裂开的果实；关于这一规律，我可以做这样的解释：除非蒴裂开，种子就不可能通过自然选择而渐次变成有翅的；结籽略微更适于吹扬的个体，比那些较不适于散布的种子占优势；蒴不开裂的，不可能进行这个过程。

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We may often falsely attribute to correlation of growth, structures which are common to whole groups of species, and which in truth are simply due to inheritance; for an ancient progenitor may have acquired through natural selection some one modification in structure, and, after thousands of generations, some other and independent modification; and these two modifications, having been transmitted to a whole group of descendants with diverse habits, would naturally be thought to be correlated in some necessary manner. So, again, I do not doubt that some apparent correlations, occurring throughout whole orders, are entirely due to the manner alone in which natural selection can act. For instance, Alph. De Candolle has remarked that winged seeds are never found in fruits which do not open: I should explain the rule by the fact that seeds could not gradually become winged through natural selection, except in fruits which opened; so that the individual plants producing seeds which were a little better fitted to be wafted further, might get an advantage over those producing seed less fitted for dispersal; and this process could not possibly go on in fruit which did not open.

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老圣提雷尔和歌德几乎同时提出生长的补偿法则，即平衡法则；依照歌德所说的，“自然为了要在一边花费，就得在另一边节约。”我想，这种说法对于家养动物好歹是适用的：如果养料过多地流向一部分或一器官，那流向另一部分的养料至少不会过多；所以要获得一头既产奶多又容易长膘的牛是困难的。同一批圆白菜变种，不会产生数量营养双丰的菜叶，同时又结出大量的含油菜籽。水果种子萎缩时，果肉本身却在大小和品质方面大大地改进了。家鸡，头上有一大丛冠毛的，一般都伴随着鸡冠缩小，多须的，则伴随着肉垂缩小。对于自然状态下的物种，很难坚持普遍适用这一法则；但是许多优秀的观察者，特别是植物学者，都相信其正确性。然而，我这里不会列举任何例子，觉得很难用什么方法来辨别两种效果，一是一部分通过自然选择而大大发育，而另一邻近部分由于同样的过程或不使用却缩小了；另一是一部分的养料被实际夺取，而另一邻近部分过分生长。

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The elder Geoffroy and Goethe propounded, at about the same period, their law of compensation or balancement of growth; or, as Goethe expressed it, “in order to spend on one side, nature is forced to economise on the other side.” I think this holds true to a certain extent with our domestic productions: if nourishment flows to one part or organ in excess, it rarely flows, at least in excess, to another part; thus it is difficult to get a cow to give much milk and to fatten readily. The same varieties of the cabbage do not yield abundant and nutritious foliage and a copious supply of oil-bearing seeds. When the seeds in our fruits become atrophied, the fruit itself gains largely in size and quality. In our poultry, a large tuft of feathers on the head is generally accompanied by a diminished comb, and a large beard by diminished wattles. With species in a state of nature it can hardly be maintained that the law is of universal application; but many good observers, more especially botanists, believe in its truth. I will not, however, here give any instances, for I see hardly any way of distinguishing between the effects, on the one hand, of a part being largely developed through natural selection and another and adjoining part being reduced by this same process or by disuse, and, on the other hand, the actual withdrawal of nutriment from one part owing to the excess of growth in another and adjoining part.

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我还怀疑，某些已提出过的补偿个案，以及某些其他事实，可以合并在一个普遍原则里，即自然选择不断地试图来节约体制的每一部分。多变的生活条件下，如果一种构造以前有用，后来用处不大了，其发育中的些许缩小都会被自然选择抓住，因为不把养料空费在建造无用的构造上去，是有利于个体的。我考察蔓足类时大开眼界，由此才理解了一项事实，而且类似的事例是很多的：即一种蔓足类如寄生在另一蔓足类体内因而得到保护时，其外壳即背甲便几乎完全消失了。雄性四甲石砌属（Ibla）就是这种情形，寄生石砌属（Proteolepas）确实更加如此：别的蔓足类的背甲都是由非常发达的头部前端的高度重要的三个体节所构成，并且具有巨大的神经和肌肉；但寄生的和受保护的寄生石砌，其整个的头的前部却缩小到仅仅留下一点非常小的残迹，附着在具有捕捉作用的触角基部。如果寄生习性造成大而复杂的构造成为多余时，其省略步骤尽管缓慢，对于该物种的各代个体都是有决定性的利益的；因为各动物都处于生存斗争之中，会通过减少养料浪费在无用构造上，来获得维持自己的较好机会。

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I suspect, also, that some of the cases of compensation which have been advanced, and likewise some other facts, may be merged under a more general principle, namely, that natural selection is continually trying to economise in every part of the organisation. If under changed conditions of life a structure before useful becomes less useful, any diminution, however slight, in its development, will be seized on by natural selection, for it will profit the individual not to have its nutriment wasted in building up an useless structure. I can thus only understand a fact with which I was much struck when examining cirripedes, and of which many other instances could be given: namely, that when a cirripede is parasitic within another and is thus protected, it loses more or less completely its own shell or carapace. This is the case with the male Ibla, and in a truly extraordinary manner with the Proteolepas: for the carapace in all other cirripedes consists of the three highly-important anterior segments of the head enormously developed, and furnished with great nerves and muscles; but in the parasitic and protected Proteolepas, the whole anterior part of the head is reduced to the merest rudiment attached to the bases of the prehensile antennae. Now the saving of a large and complex structure, when rendered superfluous by the parasitic habits of the Proteolepas, though effected by slow steps, would be a decided advantage to each successive individual of the species; for in the struggle for life to which every animal is exposed, each individual Proteolepas would have a better chance of supporting itself, by less nutriment being wasted in developing a structure now become useless.

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因此我认为，身体的任何部分一成为多余，自然选择终会使它缩小省略，而毫不需要相应程度地使其他某一部分发达增大。反之，自然选择会完全成功地使一个器官发达增大，而不需要某一临近部分缩小，作为必要的补偿。

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Thus, as I believe, natural selection will always succeed in the long run in reducing and saving every part of the organisation, as soon as it is rendered superfluous, without by any means causing some other part to be largely developed in a corresponding degree. And, conversely, that natural selection may perfectly well succeed in largely developing any organ, without requiring as a necessary compensation the reduction of some adjoining part.

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正如小圣提雷尔说过的，无论物种还是变种，凡是同一个体的任何部分或器官重复多次（如蛇的脊椎骨，多雄蕊花中的雄蕊），它的数量就容易变异；而同样的部分或器官数量较少的，就会保持稳定，这似乎已成惯例。这位作者以及一些植物学者还进一步指出，凡是重复的器官，在构造上极易发生变异。用欧文教授的用语来说，这叫作“生长的重复”（vegetative repetition），似乎是低等体制的标示。前面所说的似乎和学者们的普遍意见相关，自然系统中低级的生物比高级的生物容易变异。我这里所谓低等的意思是指体制的若干部分很少有机能专门化，只要同一器官不得不担任多样化工作时，大概能理解其为什么容易变异，也就是自然选择对于各种器官形状上的小偏差，无论保存或排斥，都比较宽松，不像对于专营一种功能的部分那样严格。这正如一把切割各种东西的刀子，差不多具有任何形状都可以；反之，专为切割某一特殊物体的工具，最好具有特殊的形状。千万不要忘记，自然选择只能通过和为了各生物的利益，才能在各部分发生作用。

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It seems to be a rule, as remarked by Is. Geoffroy St. Hilaire, both in varieties and in species, that when any part or organ is repeated many times in the structure of the same individual (as the vertebrae in snakes, and the stamens in polyandrous flowers) the number is variable; whereas the number of the same part or organ, when it occurs in lesser numbers, is constant. The same author and some botanists have further remarked that multiple parts are also very liable to variation in structure. Inasmuch as this “vegetative repetition,” to use Professor Owen’s expression, seems to be a sign of low organisation; the foregoing remark seems connected with the very general opinion of naturalists, that beings low in the scale of nature are more variable than those which are higher. I presume that lowness in this case means that the several parts of the organisation have been but little specialised for particular functions; and as long as the same part has to perform diversified work, we can perhaps see why it should remain variable, that is, why natural selection should have preserved or rejected each little deviation of form less carefully than when the part has to serve for one special purpose alone. In the same way that a knife which has to cut all sorts of things may be of almost any shape; whilst a tool for some particular object had better be of some particular shape. Natural selection, it should never be forgotten, can act on each part of each being, solely through and for its advantage.

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正如某些作者所说的，我想是正确的，退化器官高度容易变异。以后还要讲到退化器官和发育不全器官的一般主题，这里只补充一点，其变异性似乎是由于它们毫无用处，因而也是由于自然选择无力抑制它们构造上的偏差而已。因此，退化部分任由各种生长法则发挥，受到长期废弃的影响，受到返祖倾向的支配。

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rudimentary parts, it has been stated by some authors, and I believe with truth, are apt to be highly variable. We shall have to recur to the general subject of rudimentary and aborted organs; and I will here only add that their variability seems to be owing to their uselessness, and therefore to natural selection having no power to check deviations in their structure. Thus rudimentary parts are left to the free play of the various laws of growth, to the effects of long-continued disuse, and to the tendency to reversion.

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比起近似物种里的同一部分，任何一个物种的异常发达的部分易高度变异。——数年前，我被沃特豪斯先生发表的与上面标题近似的论点所打动。从欧文教授关于婆罗洲野人手臂长度的观察，我推理他也似乎得出了近似的结论。要使人相信上述主张的正确性，不把我所搜集的一系列事实举出来是无望的，然而不可能在这里和盘托出。我只能说，我坚信这是一个极普遍的规律。我考虑到可能发生错误的几种原因，但希望我已对它们留下了足够的余地。必须明白，对于任何身体部分，即使是异常发达的部分，除非和许多密切近似物种的同一部分比较，显示出它异常发达，就不能应用这一规律。例如蝙蝠的翅膀，在哺乳动物纲中是一个最异常的构造，但这里并不能应用这一规律，因为一大群的蝙蝠都有翅膀；只有某一蝙蝠物种和同属的其他物种相比较，具有显著发达的翅膀，才能应用。在第二性征以任何异常方式出现的情况下，可以大大地应用这一规律。亨特（Hunter）所用的第二性征这一术语，是指属于雌雄一方的性状，但与生殖行为并无直接关系。这一规律适用于雄性和雌性，但雌性适用比较少，因为很少具有显著的第二性征。这一规律很明显适用于第二性征，可能是由于这些性状不论是否以异常的方式出现，总是具有巨大变异性——我想这毋庸置疑。但是这一规律并不局限于第二性征，雌雄同体的蔓足类就是明证。这里补充一下，我研究这一目时，特别注意了沃特豪斯的话；我坚信，这一规律几乎总是适用蔓足目。我将在未来的著作里，把显著的个案都列成一个表；这里只举出一个个案，说明这一规律的最大适用实例。无柄蔓足类（岩藤壶）的盖瓣，从各方面说都是很重要的构造，甚至在不同的属里它们的差异也极小；但有一属，即在四甲藤壶属（Pyrgoma）的若干物种里，这些瓣却呈现惊人的多样性；这种同源的瓣，形状有时在异种之间竟完全不同；而且在同种个体间，其变异量也非常之大，可以不夸张地说，这些重要器官在同种各变种间所表现的性状差异，大于异属间所表现的。

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A part developed in any species in an extraordinary degree or manner, in comparison with the same part in allied species, tends to be highly variable.—Several years ago I was much struck with a remark, nearly to the above effect, published by Mr. Waterhouse. I infer also from an observation made by Professor Owen, with respect to the length of the arms of the ourang-outang, that he has come to a nearly similar conclusion. It is hopeless to attempt to convince any one of the truth of this proposition without giving the long array of facts which I have collected, and which cannot possibly be here introduced. I can only state my conviction that it is a rule of high generality. I am aware of several causes of error, but I hope that I have made due allowance for them. It should be understood that the rule by no means applies to any part, however unusually developed, unless it be unusually developed in comparison with the same part in closely allied species. Thus, the bat’s wing is a most abnormal structure in the class mammalia; but the rule would not here apply, because there is a whole group of bats having wings; it would apply only if some one species of bat had its wings developed in some remarkable manner in comparison with the other species of the same genus. The rule applies very strongly in the case of secondary sexual characters, when displayed in any unusual manner. The term, secondary sexual characters, used by Hunter, applies to characters which are attached to one sex, but are not directly connected with the act of reproduction. The rule applies to males and females; but as females more rarely offer remarkable secondary sexual characters, it applies more rarely to them. The rule being so plainly applicable in the case of secondary sexual characters, may be due to the great variability of these characters, whether or not displayed in any unusual manner—of which fact I think there can be little doubt. But that our rule is not confined to secondary sexual characters is clearly shown in the case of hermaphrodite cirripedes; and I may here add, that I particularly attended to Mr. Waterhouse’s remark, whilst investigating this Order, and I am fully convinced that the rule almost invariably holds good with cirripedes. I shall, in my future work, give a list of the more remarkable cases; I will here only briefly give one, as it illustrates the rule in its largest application. The opercular valves of sessile cirripedes (rock barnacles) are, in every sense of the word, very important structures, and they differ extremely little even in different genera; but in the several species of one genus, Pyrgoma, these valves present a marvellous amount of diversification: the homologous valves in the different species being sometimes wholly unlike in shape; and the amount of variation in the individuals of several of the species is so great, that it is no exaggeration to state that the varieties differ more from each other in the characters of these important valves than do other species of distinct genera.

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栖息在同一地方的鸟类变异极小，我曾特别注意到它们；这一规律似乎是肯定适用于这一纲的。我还不能发现这一规律可以应用于植物，若不是植物的巨大变异性使得它们变异性的相对程度特别难以比较，我对这一规律正确性的信赖就要发生严重的动摇。

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As birds within the same country vary in a remarkably small degree, I have particularly attended to them, and the rule seems to me certainly to hold good in this class. I cannot make out that it applies to plants, and this would seriously have shaken my belief in its truth, had not the great variability in plants made it particularly difficult to compare their relative degrees of variability.

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看到一个物种的任何部分或器官以显著的程度或方式发育时，正当的假定是，它对于那一物种是高度重要的；然而这时该部分极易变异。为什么如此呢？根据各个物种独立创造出来的观点，即所有部分都像今天所看到的那样，我找不出什么解释。但根据各个物种群是从其他物种传下来并且通过自然选择而发生了变异的观点，我想就能得到一些启发。如果我们对于家养动物的任何部分或整体不予注意，而不施任何选择，那这一部分（例如，多径鸡［Dorking fowl］的肉冠），或整个品种，就不会再有近乎一致的性状。可以说这一品种是退化了。在残迹器官方面，在很少功用专门化的器官方面，也许在多形的类群方面，我们可以看到几乎平行的自然个案；此时，自然选择未曾或者不能发生充分的作用，因此体制便处于彷徨的状态。但是这里我们特别关心的是，在家养动物里，那些由于连续的选择作用而现今正在迅速变化的方面也是显著易于变异的。看一看鸽子的品种吧，不同翻飞鸽的嘴、不同传书鸽的嘴和肉垂、扇尾鸽的姿态及尾羽等等具有何等巨大的差异量；这些正是目前英国养鸽者主要注意的方面。甚至在同一个亚品种里，如短面翻飞鸽，众所周知要育成近乎完全标准的鸽子是极困难的，新生个体往往与标准相去甚远。因此可以说，一方面要回到较不完全变异状态去的倾向，以及进一步发生各种变异的内在倾向；一方面是保持品种纯真的不断选择的力量，两者每时每刻在进行着斗争。长远看还是选择获胜，因此我们不必担心无法从优良的短面鸽品系里育出像普通翻飞鸽那样粗劣的鸽子。不过，只要选择正在迅速进行，正在进行变异的构造总会出现巨大的变异性。还应该注意，这些人类选择所引起的可变异性状，有时候会莫名其妙地专门附着于一个性别，一般是雄性，比如传书鸽的肉垂和球胸鸽的大嗉子。

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When we see any part or organ developed in a remarkable degree or manner in any species, the fair presumption is that it is of high importance to that species; nevertheless the part in this case is eminently liable to variation. Why should this be so? On the view that each species has been independently created, with all its parts as we now see them, I can see no explanation. But on the view that groups of species have descended from other species, and have been modified through natural selection, I think we can obtain some light. In our domestic animals, if any part, or the whole animal, be neglected and no selection be applied, that part (for instance, the comb in the Dorking fowl) or the whole breed will cease to have a nearly uniform character. The breed will then be said to have degenerated. In rudimentary organs, and in those which have been but little specialised for any particular purpose, and perhaps in polymorphic groups, we see a nearly parallel natural case; for in such cases natural selection either has not or cannot come into full play, and thus the organisation is left in a fluctuating condition. But what here more especially concerns us is, that in our domestic animals those points, which at the present time are undergoing rapid change by continued selection, are also eminently liable to variation. Look at the breeds of the pigeon; see what a prodigious amount of difference there is in the beak of the different tumblers, in the beak and wattle of the different carriers, in the carriage and tail of our fantails, etc., these being the points now mainly attended to by English fanciers. Even in the sub-breeds, as in the short-faced tumbler, it is notoriously difficult to breed them nearly to perfection, and frequently individuals are born which depart widely from the standard. There may be truly said to be a constant struggle going on between, on the one hand, the tendency to reversion to a less modified state, as well as an innate tendency to further variability of all kinds, and, on the other hand, the power of steady selection to keep the breed true. In the long run selection gains the day, and we do not expect to fail so far as to breed a bird as coarse as a common tumbler from a good short- faced strain. But as long as selection is rapidly going on, there may always be expected to be much variability in the structure undergoing modification. It further deserves notice that these variable characters, produced by man’s selection, sometimes become attached, from causes quite unknown to us, more to one sex than to the other, generally to the male sex, as with the wattle of carriers and the enlarged crop of pouters.

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现在让我们转向自然界。任何一个物种的一个部分如果比同属的其他物种异常发达，我们就可以断言，这一部分自从该属的共同祖先分出的时期以来，已经进行了异乎寻常的变异。这一时期很少会极其久远，一个物种很少能持续一个地质时代以上。所谓异常的变异量是指非常巨大的长期变异性而言，是自然选择为了物种的利益而连续累积起来的。但是异常发达的部分或器官的变异性，既已如此巨大而且是在不很久远的时期内长久连续进行，我们一般还可发现，这些器官比在更长久时期内几乎保持稳定的体制的其他部分，具有更大的变异性。我坚信事实就是这样。一方面是自然选择，另一方面是返祖和变异的倾向，两者之间的斗争经过一个时期会停止下来；最异常发达的器官会成为稳定的，我认为毋庸置疑。因此，一种器官不管怎样异常，既以近于大致同一状态传递给许多变异后代，如蝙蝠的翅膀，按照我的理论来讲，它一定在很长久的时期内保持着差不多同样的状态；这样，它就并不比任何其他构造更易于变异。只有在变异是比较新近而且异常巨大的情况下，我们才能发现所谓发育的变异性（generative variability）依然高度存在。因为在这种情形下，由于对那些按照所要求的方式和程度发生变异的个体进行继续选择，而且对返归以前较少变异的状态进行继续排除，变异性很少固定下来。

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Now let us turn to nature. When a part has been developed in an extraordinary manner in any one species, compared with the other species of the same genus, we may conclude that this part has undergone an extraordinary amount of modification, since the period when the species branched off from the common progenitor of the genus. This period will seldom be remote in any extreme degree, as species very rarely endure for more than one geological period. An extraordinary amount of modification implies an unusually large and long-continued amount of variability, which has continually been accumulated by natural selection for the benefit of the species. But as the variability of the extraordinarily-developed part or organ has been so great and long-continued within a period not excessively remote, we might, as a general rule, expect still to find more variability in such parts than in other parts of the organisation, which have remained for a much longer period nearly constant. And this, I am convinced, is the case. That the struggle between natural selection on the one hand, and the tendency to reversion and variability on the other hand, will in the course of time cease; and that the most abnormally developed organs may be made constant, I can see no reason to doubt. Hence when an organ, however abnormal it may be, has been transmitted in approximately the same condition to many modified descendants, as in the case of the wing of the bat, it must have existed, according to my theory, for an immense period in nearly the same state; and thus it comes to be no more variable than any other structure. It is only in those cases in which the modification has been comparatively recent and extraordinarily great that we ought to find the generative variability, as it may be called, still present in a high degree. For in this case the variability will seldom as yet have been fixed by the continued selection of the individuals varying in the required manner and degree, and by the continued rejection of those tending to revert to a former and less modified condition.

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这里所讨论的原理可以推而广之。众所周知，物种的性状比属的性状更易变异。举一个简单的例子来说明。如果在植物大属里，有些物种开蓝花，有些物种开红花，这颜色只是物种的一种性状；开蓝花的物种会变为开红花的物种，对此谁都不会感到惊奇，反之亦然；但是，如果一切物种都是开蓝花的，这颜色就成为属的性状，而它的变异便是更异常的事情了。我选取这个例子，是因为多数学者所提出的解释不能在这里应用，他们认为物种的性状之所以比属的性状更易变异，是因为其分类所根据的那些部分，其生理重要性小于属的分类所根据的那些部分。我认为这种解释部分正确，只是间接的；在“分类”一章里还要讲到这一点。引证支持物种的性状比属的性状更易变异的说法，几乎是多此一举；但我在博物学著作里一再注意到，当作者惊奇地谈到，某一重要器官或部分在物种大群中一般是极其固定的，但在亲缘密切的物种中差异却很大，而且它在某些同种的个体中常常易于变异。这一事实表明，一般具有属的价值的性状，一经降低其价值而变为只有物种的价值时，虽然其生理重要性还保持一样，但它却往往变为易于变异的了。同样的情形大概也可以应用于畸形：至少小圣提雷尔似乎毫不怀疑，一种器官越是在同群的不同物种中正常地表现差异，在个体中也越容易变态。

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The principle included in these remarks may be extended. It is notorious that specific characters are more variable than generic. To explain by a simple example what is meant. If some species in a large genus of plants had blue flowers and some had red, the colour would be only a specific character, and no one would be surprised at one of the blue species varying into red, or conversely; but if all the species had blue flowers, the colour would become a generic character, and its variation would be a more unusual circumstance. I have chosen this example because an explanation is not in this case applicable, which most naturalists would advance, namely, that specific characters are more variable than generic, because they are taken from parts of less physiological importance than those commonly used for classing genera. I believe this explanation is partly, yet only indirectly, true; I shall, however, have to return to this subject in our chapter on Classification. It would be almost superfluous to adduce evidence in support of the above statement, that specific characters are more variable than generic; but I have repeatedly noticed in works on natural history, that when an author has remarked with surprise that some important organ or part, which is generally very constant throughout large groups of species, has differed considerably in closely-allied species, that it has, also, been variable in the individuals of some of the species. And this fact shows that a character, which is generally of generic value, when it sinks in value and becomes only of specific value, often becomes variable, though its physiological importance may remain the same. Something of the same kind applies to monstrosities: at least Is. Geoffroy St. Hilaire seems to entertain no doubt, that the more an organ normally differs in the different species of the same group, the more subject it is to individual anomalies.

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按照各个物种独立创造的流俗观点来看，在独立创造的同属各物种之间，为什么构造上相异的部分比密切近似的部分更容易变异？我看对此无法做出任何说明。但是，按照物种只是特征显著的和固定的变种的观点来看，当然就可以常常看到，在比较近期内变异了的因而彼此有所差异的那些构造部分，还要继续变异。换言之，凡是属内一切物种彼此相似的、而与其他属的构造相异的各点，就叫作属的性状。这些相同性状可以归因于共同祖先的遗传，因为自然选择很少能使若干不同的物种按照完全一样的方式进行变异，因这些不同的物种已经适于多少广泛不同的习性。所谓属的性状是在物种最初从共同祖先分出来以前就已经遗传下来了，此后它们没有发生什么变异，或者只出现了些许的差异，所以时至今日就不大会变异了。另一方面，同属某物种与另一物种的不同各点就叫作物种的性状。这些性状是在物种从一个共同祖先分出来以后，发生了变异并且出现了差异，所以大概还应在某种程度上常常发生变异——至少比长久保持稳定的那些体制的部分，更易变异。

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On the ordinary view of each species having been independently created, why should that part of the structure, which differs from the same part in other independently-created species of the same genus, be more variable than those parts which are closely alike in the several species? I do not see that any explanation can be given. But on the view of species being only strongly marked and fixed varieties, we might surely expect to find them still often continuing to vary in those parts of their structure which have varied within a moderately recent period, and which have thus come to differ. Or to state the case in another manner:—the points in which all the species of a genus resemble each other, and in which they differ from the species of some other genus, are called generic characters; and these characters in common I attribute to inheritance from a common progenitor, for it can rarely have happened that natural selection will have modified several species, fitted to more or less widely-different habits, in exactly the same manner: and as these so-called generic characters have been inherited from a remote period, since that period when the species first branched off from their common progenitor, and subsequently have not varied or come to differ in any degree, or only in a slight degree, it is not probable that they should vary at the present day. On the other hand, the points in which species differ from other species of the same genus, are called specific characters; and as these specific characters have varied and come to differ within the period of the branching off of the species from a common progenitor, it is probable that they should still often be in some degree variable,—at least more variable than those parts of the organisation which have for a very long period remained constant.

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关于现在的主题，我只想再说两句话。我想无须详细讨论，大家都会承认，第二性征是高度变异的。同时还会承认，同群的物种彼此之间在第二性征上的差异，比在体制的其他部分上的差异更加广泛。例如，比较一下在第二性征方面有强烈表现的雄性鹑鸡类之间的差异量与雌性鹑鸡类之间的差异量，此说的正确性便一目了然。第二性征的原始变异性的原因还不明显；但我们可以知道，为什么它们没有像其他部分那样表现了固定性和一致性，因为它们是性选择所积累起来的，而性选择的作用不及普通选择作用那样严格，它不致引起死亡，只是使较为不利的雄性少留一些后代而已。不管第二性征的变异性的原因是什么，因为它们是高度变异的，所以性选择就有了广阔的作用范围，因而也就能够轻易地使同群的物种在第二性征方面比在其他构造方面表现较大的差异量。

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In connexion with the present subject, I will make only two other remarks. I think it will be admitted, without my entering on details, that secondary sexual characters are very variable; I think it also will be admitted that species of the same group differ from each other more widely in their secondary sexual characters, than in other parts of their organisation; compare, for instance, the amount of difference between the males of gallinaceous birds, in which secondary sexual characters are strongly displayed, with the amount of difference between their females; and the truth of this proposition will be granted. The cause of the original variability of secondary sexual characters is not manifest; but we can see why these characters should not have been rendered as constant and uniform as other parts of the organisation; for secondary sexual characters have been accumulated by sexual selection, which is less rigid in its action than ordinary selection, as it does not entail death, but only gives fewer offspring to the less favoured males. Whatever the cause may be of the variability of secondary sexual characters, as they are highly variable, sexual selection will have had a wide scope for action, and may thus readily have succeeded in giving to the species of the same group a greater amount of difference in their sexual characters, than in other parts of their structure.

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同种两性间第二性征的差异，一般都表现在同属各物种彼此差异所在的完全相同的那一部分，这是一个值得注意的事实。关于这一事实，我愿举出列在我的表中首当其冲的两个事例来说明；由于在这些个案中，差异具有非常的性质，其关系绝不是偶然的。甲虫足部跗节的同样数目，是极大部分甲虫类所共有的一种性状；但是韦斯特伍德说，木吸虫科（Engidae）里跗节的数目变异很大；并且在同种两性间，这个数目也有差异。还有，在掘地性膜翅类里，翅脉是大部分所共有的性状，所以是高度重要的性状；但是在某些属里，翅脉因物种不同而有差异，并且在同种两性间也是如此。这种关系对于我的观点有明显的意义：我认为同属的一切物种肯定由一个共同祖先传下来，而任何一个物种的两性也一样。因此，不管共同祖先或其早期后代有哪一部分构造成为变异的，这一部分的变异极有可能要被自然选择或性选择所利用，以使各个物种在自然组成中适于各自位置，而且使同一物种的两性彼此适合，使雄性和雌性适合不同的生活习惯，或者使雄性在占有雌性方面适于和其他雄性做斗争。

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It is a remarkable fact, that the secondary sexual differences between the two sexes of the same species are generally displayed in the very same parts of the organisation in which the different species of the same genus differ from each other. Of this fact I will give in illustration two instances, the first which happen to stand on my list; and as the differences in these cases are of a very unusual nature, the relation can hardly be accidental. The same number of joints in the tarsi is a character generally common to very large groups of beetles, but in the Engidae, as Westwood has remarked, the number varies greatly; and the number likewise differs in the two sexes of the same species: again in fossorial hymenoptera, the manner of neuration of the wings is a character of the highest importance, because common to large groups; but in certain genera the neuration differs in the different species, and likewise in the two sexes of the same species. This relation has a clear meaning on my view of the subject: I look at all the species of the same genus as having as certainly descended from the same progenitor, as have the two sexes of any one of the species. Consequently, whatever part of the structure of the common progenitor, or of its early descendants, became variable; variations of this part would, it is highly probable, be taken advantage of by natural and sexual selection, in order to fit the several species to their several places in the economy of nature, and likewise to fit the two sexes of the same species to each other, or to fit the males and females to different habits of life, or the males to struggle with other males for the possession of the females.

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最后，我可以下结论，物种的性状即区别物种之间的性状，比属的性状即物种所共有的性状，具有更大的变异性；——一个物种的任何部分与同属物种的同一部分相比较，表现异常发达时，这一部分常常具有极度的变异性；一个部分无论怎样异常发达，如果这是全群物种所共有的，则其变异程度是不大的；——第二性征的变异性是大的，并且在亲缘密切的物种之间性状差异是大的；——第二性征的差异和通常的物种差异，一般都表现在体制的同一部分，——这一切原理都是紧密关联在一起的。这主要是由于，同一群物种都是一个共同祖先的后代，遗传了许多共同的东西，——由于晚近发生大量变异的部分，比遗传已久而未曾变异的部分，更加有可能继续变异下去，——由于随着时间的推移，自然选择能够好歹完全克服返祖和进一步变异的倾向，——由于性选择不及自然选择那样严格，——更由于同一部分的变异，被自然选择和性选择所积累，因此就使它适应了第二性征的目的以及一般物种的目的。

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Finally, then, I conclude that the greater variability of specific characters, or those which distinguish species from species, than of generic characters, or those which the species possess in common;—that the frequent extreme variability of any part which is developed in a species in an extraordinary manner in comparison with the same part in its congeners; and the not great degree of variability in a part, however extraordinarily it may be developed, if it be common to a whole group of species;—that the great variability of secondary sexual characters, and the great amount of difference in these same characters between closely allied species;—that secondary sexual and ordinary specific differences are generally displayed in the same parts of the organisation,—are all principles closely connected together. All being mainly due to the species of the same group having descended from a common progenitor, from whom they have inherited much in common,—to parts which have recently and largely varied being more likely still to go on varying than parts which have long been inherited and have not varied,—to natural selection having more or less completely, according to the lapse of time, overmastered the tendency to reversion and to further variability,—to sexual selection being less rigid than ordinary selection,—and to variations in the same parts having been accumulated by natural and sexual selection, and thus adapted for secondary sexual, and for ordinary specific purposes.

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不同的物种呈现相似的变异；而一个物种的变种常常表现近似物种的某种性状，或者复现早期祖代的某些性状。——观察一下家养族，就极易理解这些主张。地区相隔辽远的一些极不相同的鸽的品种，呈现头生逆毛和脚生羽毛的亚变种——这是原来的岩鸽所不曾具有的性状；所以，这些就是两个以上不同的族的相似变异。球胸鸽常有十四枝甚至十六支尾羽，可以认为是一种变异，代表了另一族即扇尾鸽的正常构造。我想不会有人怀疑，所有这些相似变异，是由于这几个鸽族都是在相似的未知影响下，从一个共同亲代遗传了相同的体质和变异倾向。植物界也有相似变异的例子，见于瑞典芜菁（Swedish turnip）和芜青甘蓝（Ruta baga）的肥大的茎（俗称根部）；若干植物学者把此等植物看作是从一个共同祖先培养出来的两个变种：如果不是这样，这个例子便成为两个所谓不同物种呈现相似变异的例子了。除此两者之外，还可加入第三者，即普通芜菁。按照每一物种是独立创造的流俗观点，势必不能把这三种植物的肥大茎的相似性，都归因于共同来源的真实原因，也不能归因于同样方式变异的倾向，而势必归因于三种分离的而又密切关联的创造行为。

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Distinct species present analogous variations; and a variety of one species often assumes some of the characters of an allied species, or reverts to some of the characters of an early progenitor.—These propositions will be most readily understood by looking to our domestic races. The most distinct breeds of pigeons, in countries most widely apart, present sub-varieties with reversed feathers on the head and feathers on the feet,—characters not possessed by the aboriginal rock-pigeon; these then are analogous variations in two or more distinct races. The frequent presence of fourteen or even sixteen tail-feathers in the pouter, may be considered as a variation representing the normal structure of another race, the fantail. I presume that no one will doubt that all such analogous variations are due to the several races of the pigeon having inherited from a common parent the same constitution and tendency to variation, when acted on by similar unknown influences. In the vegetable kingdom we have a case of analogous variation, in the enlarged stems, or roots as commonly called, of the Swedish turnip and Ruta baga, plants which several botanists rank as varieties produced by cultivation from a common parent: if this be not so, the case will then be one of analogous variation in two so-called distinct species; and to these a third may be added, namely, the common turnip. According to the ordinary view of each species having been independently created, we should have to attribute this similarity in the enlarged stems of these three plants, not to the vera causa of community of descent, and a consequent tendency to vary in a like manner, but to three separate yet closely related acts of creation.

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但是关于鸽子，还有另一个案，即所有品种会偶尔出现深蓝灰色的鸽子，翅膀有两条黑带，腰部白色，尾端有一条黑带，外羽近基部的外缘呈白色。由于所有这些标记都是亲种岩鸽的特性，我假定这是返祖个案，而不是若干品种出现新的相似变异，这是不会有人怀疑的。我想，可以有把握得出这样的结论，因为我们已经看到，这种颜色标记非常容易在两个不同的、颜色各异的品种的杂交后代中出现；在此，深蓝灰色带几种标记的重现并不来自外界生活条件的作用，而仅是依据遗传法则的杂交行为的影响。

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With pigeons, however, we have another case, namely, the occasional appearance in all the breeds, of slaty-blue birds with two black bars on the wings, a white rump, a bar at the end of the tail, with the outer feathers externally edged near their bases with white. As all these marks are characteristic of the parent rock-pigeon, I presume that no one will doubt that this is a case of reversion, and not of a new yet analogous variation appearing in the several breeds. We may I think confidently come to this conclusion, because, as we have seen, these coloured marks are eminently liable to appear in the crossed offspring of two distinct and differently coloured breeds; and in this case there is nothing in the external conditions of life to cause the reappearance of the slaty-blue, with the several marks, beyond the influence of the mere act of crossing on the laws of inheritance.

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有些性状已经失去许多世代乃至数百世代还能重现，无疑很令人惊叹。但是，当一个品种和其他品种杂交仅仅一次，其后代在许多世代中偶尔还会有复现外来品种性状的倾向——有人说大约是十二代或多至二十代。从一个祖先得来的血（用普通的说法），在十二世代后，其比例仅为两千零四十八分之一；然而，我们知道，一般认为，返祖倾向是由极少量这种外来血液所保持的。在未曾杂交过、但双亲失去了祖代某种性状的品种里，如前所述，重现失去了的性状的倾向无论强弱，差不多可以传递给无数世代，尽管可以看到反证。品种已经亡失的性状，经过许多世代以后还重复出现，最近情理的假设是，并非个体突然又酷似数百代以前的祖先，而是世世代代都有再现该性状的倾向，最后在未知的有利条件下发展起来了。例如，在很少产生蓝色黑条鸽的巴巴里家鸽里，大概每一世代都有产生蓝色羽毛的潜在倾向。这个观点是假设，但有一些事实支撑；通过无数世代传递下来的这种倾向，比十分无用的器官即残迹器官同样传递下来（我们手头有证据）的倾向，在理论上的不可能性不会更大。例如，金鱼草（snapdragon，Antirrhinum）常常出现第五雄蕊的残迹器官，它一定有该遗传的倾向。

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No doubt it is a very surprising fact that characters should reappear after having been lost for many, perhaps for hundreds of generations. But when a breed has been crossed only once by some other breed, the offspring occasionally show a tendency to revert in character to the foreign breed for many generations—some say, for a dozen or even a score of generations. After twelve generations, the proportion of blood, to use a common expression, of any one ancestor, is only 1 in 2048; and yet, as we see, it is generally believed that a tendency to reversion is retained by this very small proportion of foreign blood. In a breed which has not been crossed, but in which both parents have lost some character which their progenitor possessed, the tendency, whether strong or weak, to reproduce the lost character might be, as was formerly remarked, for all that we can see to the contrary, transmitted for almost any number of generations. When a character which has been lost in a breed, reappears after a great number of generations, the most probable hypothesis is, not that the offspring suddenly takes after an ancestor some hundred generations distant, but that in each successive generation there has been a tendency to reproduce the character in question, which at last, under unknown favourable conditions, gains an ascendancy. For instance, it is probable that in each generation of the barb-pigeon, which produces most rarely a blue and black-barred bird, there has been a tendency in each generation in the plumage to assume this colour. This view is hypothetical, but could be supported by some facts; and I can see no more abstract improbability in a tendency to produce any character being inherited for an endless number of generations, than in quite useless or rudimentary organs being, as we all know them to be, thus inherited. Indeed, we may sometimes observe a mere tendency to produce a rudiment inherited: for instance, in the common snapdragon (Antirrhinum) a rudiment of a fifth stamen so often appears, that this plant must have an inherited tendency to produce it.

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根据我的理论，同属的一切物种既然假定是从一个共同祖先传下来的，那就可以期待，它们偶尔会以相似的方式变异；所以某一物种的一个变种在某些性状上会与另一物种相似。这另一个物种，按我的观点，只是特征显著而固定的变种而已。但是单由相似变异而发生的性状，其性质大概不重要，因为一切重要性状的存在，须依照物种的不同习性，通过自然选择而决定，而不会留给生活条件与相似遗传体质的相互作用。可以进一步期待，同属的物种偶尔会重现失去的祖先性状。然而，由于不知任何类群的共同祖先的确切性状，也就不能区别这两个个案。例如，如果不知道亲种岩鸽不具毛脚或倒冠毛，我们就不能说家养品种中出现这样的性状，到底是返祖现象，还仅仅是相似变异；但我们从众多标记可以推论出，蓝色是返祖的个案，因为标记和蓝色是相关联的，看样子不会从一次简单变异中一齐出现。颜色不同的品种进行杂交时，蓝色和标记频繁出现；由此我们尤其可以推论出上述一点。因此，尽管在自然状况下，一般必须存疑，什么个案是古已存在性状的重现，什么个案是相似的新变异，然而，根据我的理论，有时应该发现一个物种的变异着的后代具有同群的其他个体已经具有的性状，不管是返祖还是相似变异。这无可怀疑是自然界的情况。

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As all the species of the same genus are supposed, on my theory, to have descended from a common parent, it might be expected that they would occasionally vary in an analogous manner; so that a variety of one species would resemble in some of its characters another species; this other species being on my view only a well-marked and permanent variety. But characters thus gained would probably be of an unimportant nature, for the presence of all important characters will be governed by natural selection, in accordance with the diverse habits of the species, and will not be left to the mutual action of the conditions of life and of a similar inherited constitution. It might further be expected that the species of the same genus would occasionally exhibit reversions to lost ancestral characters. As, however, we never know the exact character of the common ancestor of a group, we could not distinguish these two cases: if, for instance, we did not know that the rock-pigeon was not feather-footed or turn-crowned, we could not have told, whether these characters in our domestic breeds were reversions or only analogous variations; but we might have inferred that the blueness was a case of reversion, from the number of the markings, which are correlated with the blue tint, and which it does not appear probable would all appear together from simple variation. More especially we might have inferred this, from the blue colour and marks so often appearing when distinct breeds of diverse colours are crossed. Hence, though under nature it must generally be left doubtful, what cases are reversions to an anciently existing character, and what are new but analogous variations, yet we ought, on my theory, sometimes to find the varying offspring of a species assuming characters (either from reversion or from analogous variation) which already occur in some other members of the same group. And this undoubtedly is the case in nature.

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分类中识别变异物种，难处主要在于变种好像模仿同属中的其他物种。还有，介于两个类型之间的中间类型不胜枚举，而这些类型本身列为变种还是物种也还存疑；除非把所有这些类型都认为是分别创造的物种，上述一点就表明，变异中的类型已经获得了对方的某些性状，所以才产生了中间类型。但是最好的证据还在于性状一般不变的重要部分或器官，偶尔也发生变异，好歹获得近似物种的同一部分或器官的性状。我搜集了一大堆此种个案，但这里照例无缘列举。我只能重复一遍，这种个案的确存在，我看很值得注意。

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A considerable part of the difficulty in recognising a variable species in our systematic works, is due to its varieties mocking, as it were, some of the other species of the same genus. A considerable catalogue, also, could be given of forms intermediate between two other forms, which themselves must be doubtfully ranked as either varieties or species; and this shows, unless all these forms be considered as independently created species, that the one in varying has assumed some of the characters of the other, so as to produce the intermediate form. But the best evidence is afforded by parts or organs of an important and uniform nature occasionally varying so as to acquire, in some degree, the character of the same part or organ in an allied species. I have collected a long list of such cases; but here, as before, I lie under a great disadvantage in not being able to give them. I can only repeat that such cases certainly do occur, and seem to me very remarkable.

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然而，我要举出一个奇异而复杂的个案，倒不是影响了任何重要性状，而是出现在同属的若干物种里，一部分是家养的，一部分是在自然状况下的。显然属于返祖现象。驴腿上不时出现很明显的横条纹，就像斑马腿：有人声称幼驴腿最为明显，我调查后，认为千真万确。还有人声称，肩上的条纹有时是双重的，在长度和轮廓方面当然易于变异。有人说有一头白驴脊上和肩上没有条纹，这不是皮肤白化病，深色的驴子这种条纹有时也很不明显或实际上完全失去了。据说由帕拉斯命名的古骏野驴（koulan of Pallas）肩上有双重条纹。野驴没有肩条纹，但布莱斯先生等人说，偶然会出现条纹痕迹；普尔（Poole）上校告诉我说，这个物种的幼驹，一般腿上都有条纹，而肩上的条纹却很模糊。斑驴（quagga）虽然躯体部有斑马状的明显条纹，腿上却没有；然而格雷（Gray）博士所绘制的一个标本，后脚踝关节处却有极清楚的斑马状条纹。

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I will, however, give one curious and complex case, not indeed as affecting any important character, but from occurring in several species of the same genus, partly under domestication and partly under nature. It is a case apparently of reversion. The ass not rarely has very distinct transverse bars on its legs, like those on the legs of the zebra: it has been asserted that these are plainest in the foal, and from inquiries which I have made, I believe this to be true. It has also been asserted that the stripe on each shoulder is sometimes double. The shoulder-stripe is certainly very variable in length and outline. A white ass, but not an albino, has been described without either spinal or shoulder-stripe; and these stripes are sometimes very obscure, or actually quite lost, in dark-coloured asses. The koulan of Pallas is said to have been seen with a double shoulder-stripe. The hemionus has no shoulder-stripe; but traces of it, as stated by Mr. Blyth and others, occasionally appear: and I have been informed by Colonel Poole that the foals of this species are generally striped on the legs, and faintly on the shoulder. The quagga, though so plainly barred like a zebra over the body, is without bars on the legs; but Dr. Gray has figured one specimen with very distinct zebra-like bars on the hocks.

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关于马，我在英国搜集了许多极其不同品种的、各种颜色的马脊上生有条纹的个案：暗褐色和鼠褐色的马腿上生有横条纹的并不罕见，栗色马中也有过一个这样的例子；暗褐色的马有时肩上生有不明显的条纹，而且我在一匹枣红马的肩上也曾看到条纹痕迹。我的儿子为我仔细检查并速写了双肩生有双重条纹、腿部生有条纹的一匹暗褐色比利时驾车马，还有一位信得过的人替我仔细查验过一匹小型暗褐色威尔士矮种马（Welsh pony）双肩上生有三条平行的短条纹。

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With respect to the horse, I have collected cases in England of the spinal stripe in horses of the most distinct breeds, and of all colours; transverse bars on the legs are not rare in duns, mouse-duns, and in one instance in a chestnut: a faint shoulder-stripe may sometimes be seen in duns, and I have seen a trace in a bay horse. My son made a careful examination and sketch for me of a dun Belgian cart-horse with a double stripe on each shoulder and with leg-stripes; and a man, whom I can implicitly trust, has examined for me a small dun Welch pony with three short parallel stripes on each shoulder.

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印度西北部，凯替华（Kattywar）品种的马，通常都生有条纹。听普尔上校说，他曾为印度政府查验过这个品种，没有条纹的马被认为不是纯种马。脊上都生有条纹；腿上也通常生有条纹，肩上的条纹也很普通，有时候是双条，有时候是三条；还有，脸的侧面有时候也生有条纹。幼驹的条纹最明显，老马的条纹有时完全消失了。普尔上校见过初生的灰色和枣红色凯替华马都有条纹。从W. W. 爱德华先生给我的材料中，我有理由推测，幼小的英国赛马脊上条纹比长成的马普遍得多。这里无须赘述。可以说，我搜集了许多腿条纹和肩条纹的个案，表明不同地方的极其不同品种的马都有条纹，从英国到中国东部，从北方的挪威到南方的马来群岛，都是如此。在世界各地，这种条纹最常见于暗褐色和鼠褐色的马；暗褐色包括广大范围的颜色，从介于褐色和黑色中间的颜色起，一直到接近乳白色。

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In the north-west part of India the Kattywar breed of horses is so generally striped, that, as I hear from Colonel Poole, who examined the breed for the Indian Government, a horse without stripes is not considered as purely-bred. The spine is always striped; the legs are generally barred; and the shoulder-stripe, which is sometimes double and sometimes treble, is common; the side of the face, moreover, is sometimes striped. The stripes are plainest in the foal; and sometimes quite disappear in old horses. Colonel Poole has seen both gray and bay Kattywar horses striped when first foaled. I have, also, reason to suspect, from information given me by Mr. W. W. Edwards, that with the English race-horse the spinal stripe is much commoner in the foal than in the full-grown animal. Without here entering on further details, I may state that I have collected cases of leg and shoulder stripes in horses of very different breeds, in various countries from Britain to Eastern China; and from Norway in the north to the Malay Archipelago in the south. In all parts of the world these stripes occur far oftenest in duns and mouse-duns; by the term dun a large range of colour is included, from one between brown and black to a close approach to cream-colour.

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我知道史密斯（Hamilton Smith）上校曾就这个主题写过论文，认为马的若干品种是从若干原种传下来的，其中一个暗褐色的原种生有条纹；并且认为上述的外貌都因在古代与暗褐色的原种杂交所致。但我根本不相信这种说法，不愿意将它应用于天各一方、千差万别的品种，笨重的比利时驾车马，威尔士矮种马，结实的矮脚马，细长的凯替华马等等。

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I am aware that Colonel Hamilton Smith, who has written on this subject, believes that the several breeds of the horse have descended from several aboriginal species—one of which, the dun, was striped; and that the above-described appearances are all due to ancient crosses with the dun stock. But I am not at all satisfied with this theory, and should be loth to apply it to breeds so distinct as the heavy Belgian cart-horse, Welch ponies, cobs, the lanky Kattywar race, etc., inhabiting the most distant parts of the world.

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现在讲一讲马属几个物种的杂交效果。罗林（Rollin）断言，驴和马杂交所产生的普通骡子，腿上特别容易生有条纹。我见过一匹骡子，腿上条纹如此之多，任何人乍看都会把它当作斑马的杂种。马丁（W. C. Martin）先生在一篇有关马的优秀论文里，绘有类似的骡子图。我曾见过四张驴和斑马的杂种彩图，腿部极明显的条纹，远比身体其他部分为甚；其中一匹肩上生有双重条纹。莫顿（Moreton）爵士提出的一个著名杂种，是从栗色雌马和雄斑驴育成的，它甚至还有后来这雌马与黑色阿拉伯公马所产生的纯种后代，腿上都生有比纯种斑驴还要明显的横条纹。最后，还有一个极其值得注意的个案，格雷博士曾绘制过驴子和野驴的杂种（他告诉我，他还知道有第二个个案）；虽然驴极少腿上生有条纹，而野驴则没有，甚至在肩上也没有条纹，但是这杂种四条腿上仍然生有条纹，并且像威尔士矮种马的杂种一样，肩上还生有三条短条纹，甚至脸的两侧也生有一些斑马状条纹。关于最后这一事实，我坚信决不会有一条带色的条纹像普通所说的那样是偶然发生的，因此，驴和野驴的杂种脸上有条纹的事情便引导我去问普尔上校：是否条纹显著的凯替华品种的马脸上也曾有过条纹，如上所述，他的回答是肯定的。

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Now let us turn to the effects of crossing the several species of the horse-genus. Rollin asserts, that the common mule from the ass and horse is particularly apt to have bars on its legs. I once saw a mule with its legs so much striped that any one at first would have thought that it must have been the product of a zebra; and Mr. W. C. Martin, in his excellent treatise on the horse, has given a figure of a similar mule. In four coloured drawings, which I have seen, of hybrids between the ass and zebra, the legs were much more plainly barred than the rest of the body; and in one of them there was a double shoulder-stripe. In Lord Moreton’s famous hybrid from a chestnut mare and male quagga, the hybrid, and even the pure offspring subsequently produced from the mare by a black Arabian sire, were much more plainly barred across the legs than is even the pure quagga. Lastly, and this is another most remarkable case, a hybrid has been figured by Dr. Gray (and he informs me that he knows of a second case) from the ass and the hemionus; and this hybrid, though the ass seldom has stripes on its legs and the hemionus has none and has not even a shoulder-stripe, nevertheless had all four legs barred, and had three short shoulder-stripes, like those on the dun Welch pony, and even had some zebra-like stripes on the sides of its face. With respect to this last fact, I was so convinced that not even a stripe of colour appears from what would commonly be called an accident, that I was led solely from the occurrence of the face-stripes on this hybrid from the ass and hemionus, to ask Colonel Poole whether such face-stripes ever occur in the eminently striped Kattywar breed of horses, and was, as we have seen, answered in the affirmative.

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对于这些事实，我们现在怎么说呢？我们看到马属的几个不同品种，通过简单的变异，就像斑马似的腿上生有条纹，或者像驴似的肩上生有条纹。至于马，我们看到，当暗褐色——这种颜色接近于该属其他物种的一般颜色——出现时，这种倾向便表现得强烈。条纹的出现，并不伴生类型上的任何变化或任何其他新性状。我们看到，这种条纹出现的倾向，以极不相同的物种之间所产生的杂种最为强烈。现在看一看几个鸽品种的情形：它们是从具有某些条纹和其他标记的一种浅蓝色鸽子（包含两三个亚种或地方族）传下来的；如果任何品种由于简单的变异而具有浅蓝色，此等条纹和其他标记必然会重现，但其类型或性状却不会有任何其他变化。当最古老最纯粹的各种不同颜色的品种进行杂交时，我们看到杂种就有重现蓝色和条纹以及其他标记的强烈倾向。我曾说过，解释这种古老性状重现的合理假设是，在每一连续世代的幼鸽里都有重现久已失去的性状的倾向，这种倾向，由于未知的原因，有时占优势。我们刚才谈到，马属的若干物种里，幼马的条纹比老马更明显或表现得更普遍，如果把鸽的品种称为物种，其中有些是几百年来纯正地繁殖下来的，那么这种情形与马属的物种是何等并行不悖！至于我自己，我敢于自信地回顾到成千上万代以前，发现有一种动物具有斑马状的条纹，其他构造则很不相同，这就是家养马（不论它们是从一个或数个野生原种传下来的）、驴、亚洲野驴、斑驴以及斑马的共同祖先。

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What now are we to say to these several facts? We see several very distinct species of the horse-genus becoming, by simple variation, striped on the legs like a zebra, or striped on the shoulders like an ass. In the horse we see this tendency strong whenever a dun tint appears—a tint which approaches to that of the general colouring of the other species of the genus. The appearance of the stripes is not accompanied by any change of form or by any other new character. We see this tendency to become striped most strongly displayed in hybrids from between several of the most distinct species. Now observe the case of the several breeds of pigeons: they are descended from a pigeon (including two or three sub-species or geographical races) of a bluish colour, with certain bars and other marks; and when any breed assumes by simple variation a bluish tint, these bars and other marks invariably reappear; but without any other change of form or character. When the oldest and truest breeds of various colours are crossed, we see a strong tendency for the blue tint and bars and marks to reappear in the mongrels. I have stated that the most probable hypothesis to account for the reappearance of very ancient characters, is—that there is a tendency in the young of each successive generation to produce the long-lost character, and that this tendency, from unknown causes, sometimes prevails. And we have just seen that in several species of the horse-genus the stripes are either plainer or appear more commonly in the young than in the old. Call the breeds of pigeons, some of which have bred true for centuries, species; and how exactly parallel is the case with that of the species of the horse-genus! For myself, I venture confidently to look back thousands on thousands of generations, and I see an animal striped like a zebra, but perhaps otherwise very differently constructed, the common parent of our domestic horse, whether or not it be descended from one or more wild stocks, of the ass, the hemionus, quagga, and zebra.

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我推测，那些相信马属各个物种是独立创造出来的人会主张，每一物种创造出来就赋有一种变异倾向，在自然状况下和家养状况下都按这种方式变异，使得它常常像该属其他物种那样变得具有条纹；同时每一物种创造出来就赋有一种强烈的倾向，当和栖息在世界上相隔甚远的地方的物种进行杂交时，所产生的杂种在条纹方面不像自己的双亲，而像该属的其他物种。依我看来，接受这种观点，就是以假代真，至少是代之以不可知的原因。这使得上帝的工作成为区区模仿和欺骗了；还不如与老朽无知的天体演化论者一起来相信，贝类化石从来就不曾生活过，而只是在石头里创造出来以模仿生活在海边的贝类的。

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He who believes that each equine species was independently created, will, I presume, assert that each species has been created with a tendency to vary, both under nature and under domestication, in this particular manner, so as often to become striped like other species of the genus; and that each has been created with a strong tendency, when crossed with species inhabiting distant quarters of the world, to produce hybrids resembling in their stripes, not their own parents, but other species of the genus. To admit this view is, as it seems to me, to reject a real for an unreal, or at least for an unknown, cause. It makes the works of God a mere mockery and deception; I would almost as soon believe with the old and ignorant cosmogonists, that fossil shells had never lived, but had been created in stone so as to mock the shells now living on the sea-shore.

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提要。——关于变异法则，我们深为无知。能好歹阐明任何原因的，这部分或那部分为什么对亲本发生些许变异的个案，还不到百分之一。但是每当我们使用比较的方法时，就可以看出同种的变种之间的较小差异，和同属的物种之间的较大差异，都受同样法则的支配。外界生活条件，比如气候、食物等等，似乎诱发过轻微的变异。习性在产生体质的差异上，使用在器官的强化上，以及不使用在器官的削弱缩小上，似乎表现出比较强有力的效果。同源部分倾向于按同一方式进行变异，并且有合生的倾向。坚硬部分和外在部分的改变有时能影响较柔软和内在的部分。当一部分特别发达时，也许就倾向于向邻近部分吸取养料；而构造的每一部分如果被省略了而无损害，就会被省略掉。构造的早期变化可以影响后来发育起来的部分；相关生长的例子比比皆是，其性质我们还一无所知。重复部分在数量上和构造上都易于变异，大概由于这些部分没有为了任何机能而密切专门化，所以其变异没有受到自然选择的密切节制。也许由于同样的原因，低等生物比高等生物更易变异，高等生物的整个体制比较专门化了。残迹器官由于没有用处，不受自然选择的支配，所以也许易于变异。物种的性状——即若干物种从共同祖先分出来以后所发生的不同性状——比属的性状更易变异，后者遗传已久，且在这一时期内没有发生变异。在这些说明里，我们是指现今还在变异的特殊部分或器官而言，因为它们在近代发生了变异并且由此而有所区别；但第二章里还看到，同样的原理也可应用于整个个体；因为，如果一个地区发现了任何属的许多物种——就是说那里曾经有过许多变异和分化，或者说那里新的物种类型的制造曾经活跃地进行过——那么在那个地区，平均上，我们现在可以发现极多的变种或初始物种。第二性征是高度变异的，在同群的物种里彼此差异很大。体制中同一部分的变异性，一般曾被利用以产生同一物种两性间的第二性征差异，以及同属的若干物种的种间差异。任何部分或器官，与其近缘物种的同一部分或器官相比较，如果已经发达到相当的大小或异常的状态，那么自该属产生以来必定经历了异常大量的变异；由此可以理解，为什么它至今还会比其他部分有更大的变异；因为变异是一种长久持续的、缓慢的过程，自然选择在上述情况下尚未来得及克服进一步变异的倾向，以及重现较少变异状态的倾向。但是，如果具有任何异常发达器官的一个物种，变成许多变异后代的亲本——我认为这想必是一个很缓慢的过程，需要长久的时间——自然选择就会轻易地给这个器官以固定的性状，无论其发达方式是多么异常。从一个共同祖先遗传了几乎同样体质的物种，当暴露在相似的影响之下，自然就有表现相似变异的倾向，这些相同的物种偶尔会重现其古代祖先的某些性状。虽然重要的新变异不一定是由于返祖和相似变异而发生的，但此等变异会使自然界获得更加美妙而调谐的多样性。

50
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Summary.—Our ignorance of the laws of variation is profound. Not in one case out of a hundred can we pretend to assign any reason why this or that part differs, more or less, from the same part in the parents. But whenever we have the means of instituting a comparison, the same laws appear to have acted in producing the lesser differences between varieties of the same species, and the greater differences between species of the same genus. The external conditions of life, as climate and food, etc., seem to have induced some slight modifications. Habit in producing constitutional differences, and use in strengthening, and disuse in weakening and diminishing organs, seem to have been more potent in their effects. Homologous parts tend to vary in the same way, and homologous parts tend to cohere. Modifications in hard parts and in external parts sometimes affect softer and internal parts. When one part is largely developed, perhaps it tends to draw nourishment from the adjoining parts; and every part of the structure which can be saved without detriment to the individual, will be saved. Changes of structure at an early age will generally affect parts subsequently developed; and there are very many other correlations of growth, the nature of which we are utterly unable to understand. Multiple parts are variable in number and in structure, perhaps arising from such parts not having been closely specialised to any particular function, so that their modifications have not been closely checked by natural selection. It is probably from this same cause that organic beings low in the scale of nature are more variable than those which have their whole organisation more specialised, and are higher in the scale. Rudimentary organs, from being useless, will be disregarded by natural selection, and hence probably are variable. Specific characters—that is, the characters which have come to differ since the several species of the same genus branched off from a common parent—are more variable than generic characters, or those which have long been inherited, and have not differed within this same period. In these remarks we have referred to special parts or organs being still variable, because they have recently varied and thus come to differ; but we have also seen in the second Chapter that the same principle applies to the whole individual; for in a district where many species of any genus are found—that is, where there has been much former variation and differentiation, or where the manufactory of new specific forms has been actively at work—there, on an average, we now find most varieties or incipient species. Secondary sexual characters are highly variable, and such characters differ much in the species of the same group. Variability in the same parts of the organisation has generally been taken advantage of in giving secondary sexual differences to the sexes of the same species, and specific differences to the several species of the same genus. Any part or organ developed to an extraordinary size or in an extraordinary manner, in comparison with the same part or organ in the allied species, must have gone through an extraordinary amount of modification since the genus arose; and thus we can understand why it should often still be variable in a much higher degree than other parts; for variation is a long-continued and slow process, and natural selection will in such cases not as yet have had time to overcome the tendency to further variability and to reversion to a less modified state. But when a species with any extraordinarily-developed organ has become the parent of many modified descendants—which on my view must be a very slow process, requiring a long lapse of time—in this case, natural selection may readily have succeeded in giving a fixed character to the organ, in however extraordinary a manner it may be developed. Species inheriting nearly the same constitution from a common parent and exposed to similar influences will naturally tend to present analogous variations, and these same species may occasionally revert to some of the characters of their ancient progenitors. Although new and important modifications may not arise from reversion and analogous variation, such modifications will add to the beautiful and harmonious diversity of nature.

51
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不管后代和亲代之间的每一轻微差异的原因是什么——每一差异必有因——是有利于个体的差异通过自然选择的逐渐积累，才引起了构造上的一切重要变异，从而地球上无数的生物得以相互斗争，充分适应，而生生不息。

51
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Whatever the cause may be of each slight difference in the offspring from their parents—and a cause for each must exist—it is the steady accumulation, through natural selection, of such differences, when beneficial to the individual, that gives rise to all the more important modifications of structure, by which the innumerable beings on the face of this earth are enabled to struggle with each other, and the best adapted to survive.

序号 英文/音标 中文解释 更多操作

disuse

[dɪs’juːs]

n.废止

generic

[dʒə’nerɪk]

adj.一般的;普通的;共有的;没有商标的

genus

[’dʒiːnəs]

n.【生物学】属;类;种;型

hitherto

[ˌhɪðə’tuː]

adv.到目前为止;迄今

domestication

[dəˌmestɪ’keɪʃn]

n.驯服;教化

lesser

[’lesə(r)]

adj.较少的;较小的;次要的

wholly

[’həʊlli]

adv.完全地;全部地;一概

ignorance

[’ɪɡnərəns]

n.无知;愚昧

reproductive

[ˌriːprə’dʌktɪv]

adj.复制的;生殖的

deviation

[ˌdiːvi’eɪʃn]

n.偏离;出轨;背弃

cultivation

[ˌkʌltɪ’veɪʃn]

n.教化;培养;耕作

eminent

[’emɪnənt]

adj.著名的;卓越的

susceptible

[sə’septəbl]

adj.易受外界影响的;易受感染的;容许…的

chiefly

[’tʃiːfli]

adv.主要地

offspring

[’ɒfsprɪŋ]

n.后代;子孙;产物

earliest

[’ɜːliɪst]

n.最早

dim

[dɪm]

adj.暗淡的;模糊的;笨的

fleshy

[’fleʃi]

adj.肉的;多肉的

warmer

[’wɔːmə(r)]

n.取暖器;加热工人

accumulative

[ə’kjuːmjələtɪv]

adj.积聚的;累计的

quadruped

[’kwɒdruped]

n.四足动物

indirect

[ˌɪndə’rekt]

adj.间接的;迂回的

Disuse

[dɪs’juːs]

n.废止

allude

[ə’luːd]

v.暗示;暗指

enlarge

[ɪn’lɑːdʒ]

v.扩大;增大;详述

modification

[ˌmɒdɪfɪ’keɪʃn]

n.修改;修正;修饰

flap

[flæp]

n.拍打

inhabit

[ɪn’hæbɪt]

v.居住于;占据;栖息

prey

[preɪ]

n.牺牲者;被掠食者，猎物

incapable

[ɪn’keɪpəbl]

adj.无能力的;不胜任的

tarsus

[’tɑːsəs]

n.踝骨;跗跖骨;睑板

specimen

[’spesɪmən]

n.标本;样本

Egyptian

[i’dʒɪpʃn]

adj.埃及的;埃及人的

deficient

[dɪ’fɪʃnt]

adj.不足的;不充分的;有缺陷的

progenitor

[prəʊ’dʒenɪtə(r)]

n.祖先;先驱

endemic

[en’demɪk]

adj.风土的;地方的

lull

[lʌl]

v.使安静;使入睡;哄骗;平息

necessitate

[nə’sesɪteɪt]

v. 使 ... 成为必需; 迫使

habitual

[hə’bɪtʃuəl]

adj.惯常的;习惯的

subsistence

[səb’sɪstəns]

n.生存;生计;存在

mariner

[’mærɪnə(r)]

n.海员;水手

shipwreck

[’ʃɪprek]

n.遇难船;海难;船只失事

swimmer

[’swɪmə(r)]

n.游泳者

whereas

[ˌweər’æz]

conj.然而;鉴于

mole

[məʊl]

n.痣n.鼹鼠;钱鼠;间谍;凿岩机

burrow

[’bʌrəʊ]

n.(兔子等)所掘的地洞

rodent

[’rəʊdnt]

n.啮齿动物

gradual

[’ɡrædʒuəl]

adj.逐渐的;逐步的;平缓的

dissection

[daɪ’sekʃn]

n.解剖;仔细分析

membrane

[’membreɪn]

n.【C】薄膜;膜状物

adhesion

[əd’hiːʒn]

n.粘合

eyelid

[’aɪlɪd]

n.眼皮;眼睑

crabbed

[’kræbɪd]

adj.暴躁的;难辨认的;难懂的

cavern

[’kævən]

n.大洞穴

affinity

[ə’fɪnəti]

n.姻亲;密切关系;吸引力

migrate

[maɪ’ɡreɪt]

vi.迁移;迁徙;转移

recess

[rɪ’ses]

n.休息;幽深处;凹缝;壁龛;放假

gradation

[ɡrə’deɪʃn]

n.渐变;阶段;等级;刻度;元音交替

twilight

[’twaɪlaɪt]

n.黄昏;微光;含糊不清;衰落时期

obliterate

[ə’blɪtəreɪt]

v.涂去;擦去;删除;盖销(邮票等)

antenna

[æn’tenə]

n.触角;天线

blindness

[’blaɪndnəs]

n.盲目;失明;愚昧

descent

[dɪ’sent]

n.下降;下坡;家世;血统;侵袭;衰落;继承

arctic

[’ɑːktɪk]

adj.北极的;极寒的

temperate

[’tempərət]

adj.温和的;适度的;有节制的

converse

[kən’vɜːs]

n.相反的事物;逆命题

adaptation

[ˌædæp’teɪʃn]

n.改编;改编成的作品;适应;【心】(感官)适应，适应性变化

overrate

[ˌəʊvə’reɪt]

vt.评价过高;高估;估价过高

inability

[ˌɪnə’bɪləti]

n.无能;无力

habituate

[hə’bɪtjʊeɪt]

v.使习惯于

rhododendron

[ˌrəʊdə’dendrən]

n.杜鹃花

authentic

[ɔː’θentɪk]

adj.真正的;真实的;可信的;可靠的

cooler

[’kuːlə(r)]

n.冷却器

confinement

[kən’faɪnmənt]

n.拘禁;限制;分娩

fertile

[’fɜːtaɪl]

adj.肥沃的;富饶的;能繁殖的;多产的;(创造力)丰富的

mingle

[’mɪŋɡl]

vt.使混合;使结合

graft

[ɡrɑːft]

n.嫁接;移植

glacial

[’ɡleɪʃl]

adj.冰川(期)的;非常冷的;缓慢的;(人)态度不友善的

anomaly

[ə’nɒməli]

n.异常

encyclopaedia

[enˌsaɪkləʊ’piːdjə]

n.百科全书

transpose

[træn’spəʊz]

vt.调换;颠倒顺序;【数】移项

continual

[kən’tɪnjuəl]

adj.不断的;频繁的;连续的

treatise

[’triːtɪs]

n.论文;论述;故事

Jerusalem

[dʒə’ru:sələm]

n.耶路撒冷(巴勒斯坦城市)

propagate

[’prɒpəɡeɪt]

v.繁殖;增殖;传播;传送

kidney

[’kɪdni]

n.肾;腰子

frost

[frɒst]

n.霜;霜冻;严寒

seedling

[’siːdlɪŋ]

n.幼苗

hardy

[’hɑːdi]

adj.强壮的;勇敢的;能吃苦耐劳的;耐寒的

imperfect

[ɪm’pɜːfɪkt]

adj.不完美的;有缺点的;未完善的

larva

[’lɑːvə]

n.幼虫;幼体

embryo

[’embriəʊ]

n.胚胎;萌芽

homologous

[hə’mɒləɡəs]

adj.相应的;一致的;【生物】同源的

embryonic

[ˌembri’ɒnɪk]

adj.胚胎的;萌芽期的

liable

[’laɪəbl]

a. 有(法律)责任的；有义务的;

stag

[stæɡ]

n. 【美口语】单身出外交际的男人;

Homologous

[hə’mɒləɡəs]

adj.相应的;一致的;【生物】同源的

petal

[’petl]

n.花瓣

adjoin

[ə’dʒɔɪn]

v.邻接;毗连

viscus

[’vɪskəs]

n.内脏;腑脏

singular

[’sɪŋɡjələ(r)]

a. 非凡的；卓越的;

deafness

[defnəs]

n.聋

hatch

[hætʃ]

n.孵化;舱口，舱口盖

Turkish

[’tɜːkɪʃ]

n.土耳其语;土耳其人

homology

[hɒ’mɒlədʒɪ]

n.同源;相同;同系;异性同体

pick

[pɪkt]

采摘，挑选；

abnormal

[æb’nɔːml]

adj.反常的;不正常的

dermal

[’dɜːməl]

adj.皮肤的;真皮的

independently

[ˌɪndɪ’pendəntli]

adv.独立地;自立地

floret

[’flɒrət]

n.小花;小筒花

ovary

[’əʊvəri]

n.卵巢;【植】子房

accessory

[ək’sesəri]

n.附件;配件

irregular

[ɪ’reɡjələ(r)]

adj.不规则的;不整齐的;不合法的;不合规矩的

axis

[’æksɪs]

n.轴;轴线

pelargonium

[peləˈgəʊnɪəm]

n.天竺葵属的植物

abort

[ə’bɔːt]

v.流产;堕胎;中止

shorten

[’ʃɔːtn]

v.弄短;变短

exterior

[ɪk’stɪəriə(r)]

n.外部;外表;外景

advantageous

[ˌædvən’teɪdʒəs]

adj.有利的;有助的;有益的

correlate

[’kɒrəleɪt]

vt.使相互关联

founding

[’faʊndɪŋ]

n.建立;成立,

inheritance

[ɪn’herɪtəns]

n.遗传;遗产;继承;继承物

descendant

[dɪ’sendənt]

n.后裔;子孙;后代

waft

[wɒft]

v.飘浮;飘荡

dispersal

[dɪ’spɜːsl]

n.散布;传播;分散;疏散区

economize

[ɪ’kɒnəmaɪz]

v.节约;节省;有效地利用

excess

[ɪk’ses]

n.超过;过量;过剩

atrophy

[’ætrəfi]

n.萎缩;衰退;虚脱;萎缩症

wattle

[’wɒtl]

n.编条;枝条编成的篱笆;板条;皮瘤;肉垂

botanist

[’bɒtənɪst]

n.植物学家

vertebra

[’vɜːtɪbrə]

n.脊椎骨;椎骨

stamen

[’steɪmən]

n.【植】雄蕊

naturalist

[’nætʃrəlɪst]

n.自然主义者;博物学者

diversify

[daɪ’vɜːsɪfaɪ]

vt.使多样化;使变化;使不同

uselessness

[’juːsləsnəs]

n.无用;无价值;无结果

reversion

[rɪ’vɜːʃn]

n.返回;逆转;恢复;反向

hopeless

[’həʊpləs]

adj.没有希望的;绝望的;无可救药的

proposition

[ˌprɒpə’zɪʃn]

n.提议;事业;命题

allowance

[ə’laʊəns]

n.津贴

reproduction

[ˌriːprə’dʌkʃn]

n.再现;生殖

applicable

[ə’plɪkəbl]

adj.合适的

invariably

[ɪn’veəriəbli]

adv.不变地;总是;一贯地

operculum

[əʊ’pɜːkjʊləm]

n.鳃盖;藓盖;果盖

barnacle

[’bɑːnəkl]

n.藤壶;难以摆脱的人(或东西);黑雁

diversification

[daɪˌvɜːsɪfɪ’keɪʃn]

n.多元化

fowl

[faʊl]

n.禽;禽肉

degenerate

[dɪ’dʒenəreɪt]

v.退化;堕落

parallel

[’pærəlel]

adj.平行的

fluctuate

[’flʌktʃueɪt]

vi.波动;动摇;起伏

tumbler

[’tʌmblə(r)]

n.不倒翁;杂技演员;平底无脚酒杯;锁的制动栓

carriage

[’kærɪdʒ]

n.四轮马车

fantail

[’fænteɪl]

n.扇状尾;扇尾鸽

notorious

[nəʊ’tɔːriəs]

adj.臭名昭著的

coarse

[kɔːs]

adj.粗糙的;粗俗的

comparative

[kəm’pærətɪv]

adj.比较的;相当的

rejection

[rɪ’dʒekʃn]

n.拒绝;被弃;【医】排异

physiological

[ˌfɪziə’lɒdʒɪkl]

adj.生理的;生理学的

entertain

[ˌentə’teɪn]

v.娱乐;使有兴趣;招待;考虑;抱有;容纳

manifest

[’mænɪfest]

vt.显示;证实;表露

rigid

[’rɪdʒɪd]

adj.坚硬的;严格的;固执的

lapse

[læps]

n.过失;流逝;间隔;堕落;失效

revert

[rɪ’vɜːt]

vi.恢复;回复;归还

Swedish

[’swiːdɪʃ]

adj.瑞典的;瑞典人的;瑞典语的

reappear

[ˌriːə’pɪə(r)]

v.再出现

hypothetical

[ˌhaɪpə’θetɪkl]

adj.假设的;假定的

unimportant

[ˌʌnɪm’pɔːtnt]

adj.不重要的

accordance

[ə’kɔːdns]

n.一致;符合

infer

[ɪn’fɜː(r)]

vt.推断;猜测;暗示

tint

[tɪnt]

n. 色彩; 浅色; 染发剂

undoubted

[ʌn’daʊtɪd]

adj.无疑的

systematic

[ˌsɪstə’mætɪk]

adj.有系统的

mock

[mɒk]

v.嘲弄;嘲笑;模仿

transverse

[’trænzvɜːs]

adj.横向的;横放的;横切的

spinal

[’spaɪnl]

adj.脊骨的;脊髓的

Colonel

[’kɜːnl]

n.上校

foal

[fəʊl]

n.驹子

hock

[hɒk]

n.肘关节;抵押;典当;莱茵白葡萄酒

dun

[dʌn]

vt.讨债

chestnut

[’tʃesnʌt]

n.栗子;栗树;栗色;栗色马;陈词滥调;七叶树;马的胼胝

implicit

[ɪm’plɪsɪt]

adj.含蓄的;绝对的;无疑问的;固有的;无保留的;暗示的

Welsh

[welʃ]

adj.威尔士人的;威尔士语的

pony

[’pəʊni]

n.小马;小型的东西

Hamilton

[’hæmɪltən]

汉密尔顿

mule

[mjuːl]

n.骡子;固执的人;走私毒品者

Martin

[’ma:tɪn]

n.马丁(男子名)

hybrid

[’haɪbrɪd]

n.混合物;杂种;混血儿

occurrence

[ə’kʌrəns]

n.发生

deception

[dɪ’sepʃn]

n.骗局;诡计;欺诈

institute

[’ɪnstɪtjuːt]

n.学院;学会;协会

utterly

[’ʌtəli:]

adv.完全;全然;绝对

disregard

[ˌdɪsrɪ’ɡɑːd]

vt.不顾;忽视

differentiation

[ˌdɪfəˌrenʃi’eɪʃn]

n.区别;分化;变异;【数】微分

incipient

[ɪn’sɪpiənt]

adj.起初的;初期的

harmonious

[hɑː’məʊniəs]

adj.和谐的;和睦的;协调的

innumerable

[ɪ’njuːmərəbl]

adj.无数的;数不清的

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