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物种起源|The Origin of Species

第二章　自然变异|CHAPTER II　VARIATION UNDER NATURE

属类： 双语小说 【分类】其他读物 阅读：[12166]
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变异性——个体差异——存疑的物种——分布广、分散大和普通的物种变异最多——各地大属的物种比小属的物种变异更频繁——大属里许多物种就像变种，有很密切的、但不均等的相互关系，并且分布区域有限

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Variability—Individual differences—Doubtful species—Wide ranging, much diffused, and common species vary most—Species of the larger genera in any country vary more than the species of the smaller genera—Many of the species of the larger genera resemble varieties in being very closely, but unequally, related to each other, and in having restricted ranges

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把前一章所得到的各项原则应用到自然状况下的生物之前，必须简单地讨论一下，后者是否容易发生变异。要充分讨论这一问题，必须举出一长列枯燥无味的事实；不过这些我准备留到将来的著作里。这里也不讨论物种这个术语的各种定义。至今没有一项定义能使全体学者都满意；然而谈到物种的时候，他们都模糊地知道是什么意思。这术语一般含有创世作用这一未知要素。“变种”这个术语几乎也是同样地难下定义；但是几乎普遍地蕴含世系群落的意义，虽然很少能够得到证明。还有所谓畸形也难以解释，但它们逐渐变成变种。我认为畸形是指构造上某部分显著偏差而言，对于物种要么是有害的，要么是无用的，一般不加以传播。有些作者是在专门意义上来使用“变异”术语的，它的含义是直接由物理的生活条件所引起的一种变化；这种意义的“变异体”假定为不能遗传的；但是波罗的海半咸水里贝类的矮化状态、阿尔卑斯山顶的矮化植物、极北地区动物的增厚毛皮，谁能说在某些情形下至少不遗传数代呢？我认为这种情况下，该类型是可以称为变种的。

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Before applying the principles arrived at in the last chapter to organic beings in a state of nature, we must briefly discuss whether these latter are subject to any variation. To treat this subject at all properly, a long catalogue of dry facts should be given; but these I shall reserve for my future work. Nor shall I here discuss the various definitions which have been given of the term species. No one definition has as yet satisfied all naturalists; yet every naturalist knows vaguely what he means when he speaks of a species. Generally the term includes the unknown element of a distinct act of creation. The term “variety” is almost equally difficult to define; but here community of descent is almost universally implied, though it can rarely be proved. We have also what are called monstrosities; but they graduate into varieties. By a monstrosity I presume is meant some considerable deviation of structure in one part, either injurious to or not useful to the species, and not generally propagated. Some authors use the term “variation” in a technical sense, as implying a modification directly due to the physical conditions of life; and “variations” in this sense are supposed not to be inherited: but who can say that the dwarfed condition of shells in the brackish waters of the Baltic, or dwarfed plants on Alpine summits, or the thicker fur of an animal from far northwards, would not in some cases be inherited for at least some few generations? and in this case I presume that the form would be called a variety.

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此外，还有许多微小差异，都可叫作个体差异。比如我们熟悉的经常在同父母的后代中所出现的，或者在同一局限区域内栖息的同种个体中所经常观察到的而且可以设想也是这样发生的差异。没有人会假设，同种的一切个体都是在相同的模型里铸造出来的。这种个体差异对于我们十分重要，因为这为自然选择提供了材料，可以积累，就像人类在家养生物里朝着一定方向积累个体差异那样。这种个体差异，一般作用于学者们认为不重要的那些部分；但是我可以用一连串事实阐明，无论从生理学或分类学的观点来看，都必须称为重要的那些部分，有时在同种个体中也会发生变异。我相信，哪怕经验最丰富的学者也会对变异性个案之多感到惊奇，即使是构造的重要部分也不例外；只需花上若干年，就可以同我一样搜集到这种权威的材料。应该记住，分类学家很不乐意在重要性状中发现变异性，而且很少有人愿意费神去检查重要的内部器官，并在同种的许多标本间加以比较。我从来不会料到，昆虫的靠近大中央神经节的主干神经分枝，在同一个物种里会发生变异；本来还认为这种性质的变异只能缓慢地进行；然而最近卢伯克（Lubbock）爵士阐明，胭脂虫（Coccus）的主干神经具有一定程度的变异，几乎可以与树干的不规则分枝相提并论。我补充一句，这位富有哲理的学者最近还阐明，某些昆虫幼虫的肌肉绝非千篇一律。有人说重要器官决不变异，这往往是循环论证，因为正是这些人实际上把不变异的性状当作重要的（少数学者老实坦白过）。在这种观点下，自然就找不到重要器官发生变异的例子了；但在任何其他观点下，却可以确凿地举出许多例子来。

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Again, we have many slight differences which may be called individual differences, such as are known frequently to appear in the offspring from the same parents, or which may be presumed to have thus arisen, from being frequently observed in the individuals of the same species inhabiting the same confined locality. No one supposes that all the individuals of the same species are cast in the very same mould. These individual differences are highly important for us, as they afford materials for natural selection to accumulate, in the same manner as man can accumulate in any given direction individual differences in his domesticated productions. These individual differences generally affect what naturalists consider unimportant parts; but I could show by a long catalogue of facts, that parts which must be called important, whether viewed under a physiological or classificatory point of view, sometimes vary in the individuals of the same species. I am convinced that the most experienced naturalist would be surprised at the number of the cases of variability, even in important parts of structure, which he could collect on good authority, as I have collected, during a course of years. It should be remembered that systematists are far from pleased at finding variability in important characters, and that there are not many men who will laboriously examine internal and important organs, and compare them in many specimens of the same species. I should never have expected that the branching of the main nerves close to the great central ganglion of an insect would have been variable in the same species; I should have expected that changes of this nature could have been effected only by slow degrees: yet quite recently Mr. Lubbock has shown a degree of variability in these main nerves in Coccus, which may almost be compared to the irregular branching of the stem of a tree. This philosophical naturalist, I may add, has also quite recently shown that the muscles in the larvae of certain insects are very far from uniform. Authors sometimes argue in a circle when they state that important organs never vary; for these same authors practically rank that character as important (as some few naturalists have honestly confessed) which does not vary; and, under this point of view, no instance of an important part varying will ever be found: but under any other point of view many instances assuredly can be given.

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同个体差异相关的，有一点使我非常困惑：我是指有人称为“变形的”（protean）或“多形的”（polymorphic）那些属，其中的物种表现了无节制的变异量。关于这些类型应列为物种还是变种，几乎没有两个学者意见一致。可以举植物里的悬钩子属（Rubus）、蔷薇属（Rosa）、山柳菊属（Hieracium）以及昆虫类和腕足类（Brachiopod shells）的几属为例。在大多数多形的属里，有些物种具有稳定的和一定的性状。除了少数例外，在一个地方为多形的属，似乎在别处也是多形的，并且从腕足类来判断，在早先的时代也是这样的。这些事实很使人困惑，因为它们似乎阐明这种变异是独立于生活条件之外的。我猜想，在某些多形的属里所看到的变异，处于对物种是无用的或无害的构造点，因此，自然选择对于它们就不起作用，从而不能固定下来，详见后文的说明。

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There is one point connected with individual differences, which seems to me extremely perplexing: I refer to those genera which have sometimes been called “protean” or “polymorphic,” in which the species present an inordinate amount of variation; and hardly two naturalists can agree which forms to rank as species and which as varieties. We may instance Rubus, Rosa, and Hieracium amongst plants, several genera of insects, and several genera of Brachiopod shells. In most polymorphic genera some of the species have fixed and definite characters. Genera which are polymorphic in one country seem to be, with some few exceptions, polymorphic in other countries, and likewise, judging from Brachiopod shells, at former periods of time. These facts seem to be very perplexing, for they seem to show that this kind of variability is independent of the conditions of life. I am inclined to suspect that we see in these polymorphic genera variations in points of structure which are of no service or disservice to the species, and which consequently have not been seized on and rendered definite by natural selection, as hereafter will be explained.

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有些类型，在相当程度上具有物种的性状，但同其他类型密切相似，或者由中间级进同其他类型密切相关，学者们不愿列为不同的物种；其实它们在若干方面对我们是极其重要的。我们很有理由相信，这些密切亲缘的存疑类型有许多曾在本地长久持续保存它们的性状，据我们所知，和良好的真种一样天长地久。实际上，学者们能够用具有中间性状的其他类型把两个类型连接在一起，就是把一个类型当作另一个的变种；他把最普通的一个，但常常是最初记载的类型作为物种，而把另一个作为变种。可是在决定是否把一个类型作为另一类型的变种时，哪怕两者被中间连锁紧密地连接在一起，也是有严重困难的，我并不准备在这里把这些困难列举出来；即使中间连锁具有一般所假定的杂种性质，也常常不能解决这种困难。然而在很多情形下，一个类型之所以列为另一个的变种，并非因为确已找到了中间连锁，而是因为观察者采用了类推的方法，便假设中间连锁现在确在某些地方生存着，或者它们从前可能生存过；这样，就为疑惑、臆测打开了大门。

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Those forms which possess in some considerable degree the character of species, but which are so closely similar to some other forms, or are so closely linked to them by intermediate gradations, that naturalists do not like to rank them as distinct species, are in several respects the most important for us. We have every reason to believe that many of these doubtful and closely-allied forms have permanently retained their characters in their own country for a long time; for as long, as far as we know, as have good and true species. Practically, when a naturalist can unite two forms together by others having intermediate characters, he treats the one as a variety of the other, ranking the most common, but sometimes the one first described, as the species, and the other as the variety. But cases of great difficulty, which I will not here enumerate, sometimes occur in deciding whether or not to rank one form as a variety of another, even when they are closely connected by intermediate links; nor will the commonly-assumed hybrid nature of the intermediate links always remove the difficulty. In very many cases, however, one form is ranked as a variety of another, not because the intermediate links have actually been found, but because analogy leads the observer to suppose either that they do now somewhere exist, or may formerly have existed; and here a wide door for the entry of doubt and conjecture is opened.

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因此，当决定一个类型应列为物种还是变种的时候，有健全判断力、丰富经验的学者的意见，似乎是应当遵循的唯一指针。然而在许多情况下，我们必须依据大多数学者的意见来决定，因为很少有标记显著而熟知的变种不曾被至少几位能干的鉴定者列为物种的。

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Hence, in determining whether a form should be ranked as a species or a variety, the opinion of naturalists having sound judgment and wide experience seems the only guide to follow. We must, however, in many cases, decide by a majority of naturalists, for few well-marked and well-known varieties can be named which have not been ranked as species by at least some competent judges.

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具有这种存疑性质的变种所在皆是，无可争辩。把不同学者所著的几部英、法、美植物志比较一下，就可看出有何等惊人数目的类型，往往先后被列为真物种和区区变种。多方帮助我而使我感激万分的沃森（H. C. Watson）先生告诉我说，现在有182种英国植物一般被当作变种，但是过去统统都被列为物种；开列这张名单时，省略了许多细小的变种，然而它们也曾被列为物种，此外把若干高度多形的属完全省略了。在包含着最多形的类型的属之下，巴宾顿（Babington）先生列举了251个物种，而本瑟姆（Bentham）先生只列举了112个物种——就是说差额有139个存疑类型！在每次生育必须交配、具有高度移动性的动物里，分别被学者列为物种和变种的存疑类型，在同一地区很少看到，但在分隔的地区却很普通。在北美洲和欧洲，有多少鸟和昆虫，彼此差异很微，却分别被大学者或列为无可怀疑的物种，或列为变种，或常把它们称为地理族！多年前，我曾比较过、看别人比较过加拉帕戈斯群岛上鸟类的相互异同，以及这些鸟与美洲大陆的鸟的异同，深深感到物种和变种之间的区别是何等的含糊和任意。小马德拉群岛的小岛上有许多昆虫，沃拉斯顿（Wollaston）先生的力作把它们看作变种，但许多昆虫学者毫无疑问会将它们列为物种。甚至爱尔兰也有少数动物，曾被学者看作物种，但现在一般却被看作变种。若干经验丰富的鸟类学家认为英国的红松鸡只是挪威种的一个特性显著的族，然而大多数人则把它列为英国特有的非存疑物种。两个存疑类型的原产地如果相距遥远，许多学者就会把双方都列为物种；但是，有人问得好，多少距离是足够遥远的呢？如果美洲和欧洲距离足够的话，那么欧洲到亚速尔群岛、马德拉群岛、加那利群岛、爱尔兰之间的距离是否足够呢？必须承认，有许多被鉴定家认为是变种的类型，拥有着完美的物种性状，也就被另外一些鉴定家列为货真价实的物种了。但在这些术语的定义还没有得到普遍接受之前，就来讨论什么应该称为物种，什么应该称为变种，乃是无的放矢啊。

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That varieties of this doubtful nature are far from uncommon cannot be disputed. Compare the several floras of Great Britain, of France or of the United States, drawn up by different botanists, and see what a surprising number of forms have been ranked by one botanist as good species, and by another as mere varieties. Mr. H. C. Watson, to whom I lie under deep obligation for assistance of all kinds, has marked for me 182 British plants, which are generally considered as varieties, but which have all been ranked by botanists as species; and in making this list he has omitted many trifling varieties, but which nevertheless have been ranked by some botanists as species, and he has entirely omitted several highly polymorphic genera. Under genera, including the most polymorphic forms, Mr. Babington gives 251 species, whereas Mr. Bentham gives only 112,—a difference of 139 doubtful forms! Amongst animals which unite for each birth, and which are highly locomotive, doubtful forms, ranked by one zoologist as a species and by another as a variety, can rarely be found within the same country, but are common in separated areas. How many of those birds and insects in North America and Europe, which differ very slightly from each other, have been ranked by one eminent naturalist as undoubted species, and by another as varieties, or, as they are often called, as geographical races! Many years ago, when comparing, and seeing others compare, the birds from the separate islands of the Galapagos Archipelago, both one with another, and with those from the American mainland, I was much struck how entirely vague and arbitrary is the distinction between species and varieties. On the islets of the little Madeira group there are many insects which are characterized as varieties in Mr. Wollaston’s admirable work, but which it cannot be doubted would be ranked as distinct species by many entomologists. Even Ireland has a few animals, now generally regarded as varieties, but which have been ranked as species by some zoologists. Several most experienced ornithologists consider our British red grouse as only a strongly-marked race of a Norwegian species, whereas the greater number rank it as an undoubted species peculiar to Great Britain. A wide distance between the homes of two doubtful forms leads many naturalists to rank both as distinct species; but what distance, it has been well asked, will suffice? if that between America and Europe is ample, will that between the Continent and the Azores, or Madeira, or the Canaries, or Ireland, be sufficient? It must be admitted that many forms, considered by highly-competent judges as varieties, have so perfectly the character of species that they are ranked by other highly-competent judges as good and true species. But to discuss whether they are rightly called species or varieties, before any definition of these terms has been generally accepted, is vainly to beat the air.

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许多关于特征显著的变种或存疑物种的个案，很值得考虑；因为在试图决定它们的级位上，从地理分布、相似变异、杂交等方面已经展开了若干有趣的论据路线。我在这里只提出一个实例——众所周知的报春花属（primrose）和樱草（cowslip）或黄花九轮草（Primula veris）和高报春（elatior）。这些植物外表大不相同，味道不同，气味不同，开花期略微不同，生境有点不同，上山高度不同，地理分布区不同，最后是仔细的观察者盖特纳（G?rtner）多年来所做的大量实验表明，它们杂交非常困难。简直无法指望有更好的证据来证明两个类型是不同物种了。另一方面，它们由许多中间连锁联合起来，而这些连锁是否杂种是存疑的。依我看，铺天盖地的实验证据表明，它们从共同的亲种传下来，因此必须列为变种。

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Many of the cases of strongly-marked varieties or doubtful species well deserve consideration; for several interesting lines of argument, from geographical distribution, analogical variation, hybridism, etc., have been brought to bear on the attempt to determine their rank. I will here give only a single instance,—the well-known one of the primrose and cowslip, or Primula veris and elatior. These plants differ considerably in appearance; they have a different flavour and emit a different odour; they flower at slightly different periods; they grow in somewhat different stations; they ascend mountains to different heights; they have different geographical ranges; and lastly, according to very numerous experiments made during several years by that most careful observer G?rtner, they can be crossed only with much difficulty. We could hardly wish for better evidence of the two forms being specifically distinct. On the other hand, they are united by many intermediate links, and it is very doubtful whether these links are hybrids; and there is, as it seems to me, an overwhelming amount of experimental evidence, showing that they descend from common parents, and consequently must be ranked as varieties.

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在大多数情形下，过细的调查可以使学者们对存疑类型的分级取得一致的意见。然而必须坦言，在研究得最透彻的地区，所见到的存疑类型的数目也最多。我惊异地发现，如果自然状况下的任何动植物对人极有用，或为了任何原因能引起人们的密切注意，那么它的变种就几乎普遍地记载下来了。而且这些变种往往被某些作者列为物种。看看普通的栎树（oak），研究得何等精细呀；然而，一位德国作者竟从其他学者普遍认为是变种的类型中确定了十二个以上的物种；在英国，可以举出一些植物学的最高权威和实际工作者，有的认为无梗的和有梗的栎树是物种，有的仅仅认为它们是变种。

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Close investigation, in most cases, will bring naturalists to an agreement how to rank doubtful forms. Yet it must be confessed, that it is in the best-known countries that we find the greatest number of forms of doubtful value. I have been struck with the fact, that if any animal or plant in a state of nature be highly useful to man, or from any cause closely attract his attention, varieties of it will almost universally be found recorded. These varieties, moreover, will be often ranked by some authors as species. Look at the common oak, how closely it has been studied; yet a German author makes more than a dozen species out of forms, which are very generally considered as varieties; and in this country the highest botanical authorities and practical men can be quoted to show that the sessile and pedunculated oaks are either good and distinct species or mere varieties.

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青年学者开始研究陌生的生物类群时，倍感困惑的首先就是决定什么是物种的差异，什么是变种的差异。他对这个生物类群所发生的变异量和变异种类一无所知；这至少可以表明，生物发生某种变异是多么普遍。但是，如果把注意力集中于一个地区里的某一类生物，就会很快决定如何去分级大部分的存疑类型。他一般倾向于定出许多物种，就像前文讲过的养鸽和养鸡爱好者那样，他所不断研究着的那些类型的差异量将会给他深刻的印象；而在其他地区和其他生物类群的相似变异方面他缺少一般知识，无法用来校正他的最初印象。等到他扩大了观察范围，就会遇到更多困难；他将遇到数目更多的密切近似类型。但是，如果进一步扩大他的观察范围，最后将能够有所决定何谓变种，何谓物种；不过他要在这方面获得成功，代价是承认大量变异，然而这样承认是否正确，往往会引起其他学者的争议。何况，如果从现今已不连续的地区找来亲缘类型加以研究，他就没有希望找到存疑类型的中间连锁，于是不得不几乎完全依赖类推的方法，这就会使他的困难登峰造极。

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When a young naturalist commences the study of a group of organisms quite unknown to him, he is at first much perplexed to determine what differences to consider as specific, and what as varieties; for he knows nothing of the amount and kind of variation to which the group is subject; and this shows, at least, how very generally there is some variation. But if he confine his attention to one class within one country, he will soon make up his mind how to rank most of the doubtful forms. His general tendency will be to make many species, for he will become impressed, just like the pigeon or poultry-fancier before alluded to, with the amount of difference in the forms which he is continually studying; and he has little general knowledge of analogical variation in other groups and in other countries, by which to correct his first impressions. As he extends the range of his observations, he will meet with more cases of difficulty; for he will encounter a greater number of closely-allied forms. But if his observations be widely extended, he will in the end generally be enabled to make up his own mind which to call varieties and which species; but he will succeed in this at the expense of admitting much variation,—and the truth of this admission will often be disputed by other naturalists. When, moreover, he comes to study allied forms brought from countries not now continuous, in which case he can hardly hope to find the intermediate links between his doubtful forms, he will have to trust almost entirely to analogy, and his difficulties will rise to a climax.

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在物种和亚种之间，当然还没有划出过明确的界限——亚种就是类型里面有些学者认为已很接近物种，但还没有完全达到物种那一级；还有，在亚种和显著的变种之间，在较不显著的变种和个体差异之间也是一笔糊涂账。这些差异被一个不易察觉的系列彼此混合，而该系列令人产生存在实际过渡的印象。

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Certainly no clear line of demarcation has as yet been drawn between species and sub-species—that is, the forms which in the opinion of some naturalists come very near to, but do not quite arrive at the rank of species; or, again, between sub-species and well-marked varieties, or between lesser varieties and individual differences. These differences blend into each other in an insensible series; and a series impresses the mind with the idea of an actual passage.

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因此，我认为，个体差异虽对分类学家无足轻重，但对我们却很重要，这是分辨轻度变种的第一步，而博物学著作认为不值得记载那些变种。我认为，任何程度上比较显著、比较永久的变种都是走向更显著、更永久变种的步骤；而后者是走向亚种，走向物种的步骤。从一个阶段的差异到另一个高级阶段的过渡，在某种情况下，可能仅仅是由于长久连续居于两个不同地区不同物理条件之下的结果；但这种观点使我信心不足。我把一个变种从略不同于亲种的状态到更加不同的状态的过渡，归因于自然选择的累积（容以后详论）作用，在某个确定的方向积累构造的差异。所以我认为显著的变种可以理直气壮地叫作初始物种；但是这种观点是否合理，必须根据本书所举出的各种事实和论点，通盘权衡，加以判断。

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Hence I look at individual differences, though of small interest to the systematist, as of high importance for us, as being the first step towards such slight varieties as are barely thought worth recording in works on natural history. And I look at varieties which are in any degree more distinct and permanent, as steps leading to more strongly marked and more permanent varieties; and at these latter, as leading to sub-species, and to species. The passage from one stage of difference to another and higher stage may be, in some cases, due merely to the long-continued action of different physical conditions in two different regions; but I have not much faith in this view; and I attribute the passage of a variety, from a state in which it differs very slightly from its parent to one in which it differs more, to the action of natural selection in accumulating (as will hereafter be more fully explained) differences of structure in certain definite directions. Hence I believe a well-marked variety may be justly called an incipient species; but whether this belief be justifiable must be judged of by the general weight of the several facts and views given throughout this work.

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不必设想一切变种或初始物种都能达到物种的一级。它们也许会在初始状态中绝灭，或者长时期地停留在变种的阶段，如沃拉斯顿先生所指出的马德拉地方某些化石陆地贝类的变种便是这样。如果一个变种很繁盛，而超过了亲种的数目，那就会列为物种，而亲种就当作变种了；或者它会淘汰消灭亲种；或者两者并存，都排列为独立的物种。我们以后还要回来讨论这一问题。

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It need not be supposed that all varieties or incipient species necessarily attain the rank of species. They may whilst in this incipient state become extinct, or they may endure as varieties for very long periods, as has been shown to be the case by Mr. Wollaston with the varieties of certain fossil land-shells in Madeira. If a variety were to flourish so as to exceed in numbers the parent species, it would then rank as the species, and the species as the variety; or it might come to supplant and exterminate the parent species; or both might co-exist, and both rank as independent species. But we shall hereafter have to return to this subject.

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从上述可以看出，我认为物种这个术语是为了便利而任意加于一群互相密切类似的个体的，它和变种这个术语在本质上并没有区别，变种是指区别较少而波动较多的类型。还有，变种这个名词和个体差异比较，也是为了便利而任意取用的。

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From these remarks it will be seen that I look at the term species, as one arbitrarily given for the sake of convenience to a set of individuals closely resembling each other, and that it does not essentially differ from the term variety, which is given to less distinct and more fluctuating forms. The term variety, again, in comparison with mere individual differences, is also applied arbitrarily, and for mere convenience sake.

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在理论的指导下，我曾经想，将若干编著完备的植物志中的所有变种排列成表，对于变化最多的物种的性质和关系，也许能获得一些有趣的结果。乍看，这似乎是一件简单的工作；但是，不久沃森先生使我相信其中难点重重，我深深感谢他在这个问题上的宝贵忠告和帮助，以后胡克博士也这么说，甚至语气更重。这些难点和各变异物种的比例数目表，将留在将来的著作里再予讨论。胡克博士细读了我的原稿，检查了表格之后，他允许我补充说明，他认为下面的论述可以成立。然而，这里虽然讲得很简单，但整个问题是相当令人困惑的，并且不能不涉及“生存斗争”“性状的分歧”等问题，容以后讨论。

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Guided by theoretical considerations, I thought that some interesting results might be obtained in regard to the nature and relations of the species which vary most, by tabulating all the varieties in several well-worked floras. At first this seemed a simple task; but Mr. H. C. Watson, to whom I am much indebted for valuable advice and assistance on this subject, soon convinced me that there were many difficulties, as did subsequently Dr. Hooker, even in stronger terms. I shall reserve for my future work the discussion of these difficulties, and the tables themselves of the proportional numbers of the varying species. Dr. Hooker permits me to add, that after having carefully read my manuscript, and examined the tables, he thinks that the following statements are fairly well established. The whole subject, however, treated as it necessarily here is with much brevity, is rather perplexing, and allusions cannot be avoided to the “struggle for existence,” “divergence of character,” and other questions, hereafter to be discussed.

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德康多尔等人阐明，分布很广的植物一般会出现变种；这在意料之中，因为暴露在不同的物理条件之下，还要和各类不同的生物进行竞争（以后将看到，这一点是更重要的条件）。但是我的表格进一步阐明，在任何有限制的地区里，越是普通的物种，即个体越多的物种，以及在自己的区域内分散越广的物种（这和分布广的意义不同，和普通也略有不同），往往发生特征足够显著的变种，记载在植物学著作中。因此，越是繁盛的物种，或者称为优势物种——它们分布最广，在本区域内分散最广，个体最多——就越产生显著的变种，或我所称的初始物种。这也许在预料之中，因为作为变种，要在任何程度上变成永久，必定要和该区域内的其他居住者进行斗争；已经占优势的物种，最有可能产生特定后代，虽然有轻微变异，还是继承了使亲种战胜同地生物的那些优点。

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Alph. De Candolle and others have shown that plants which have very wide ranges generally present varieties; and this might have been expected, as they become exposed to diverse physical conditions, and as they come into competition (which, as we shall hereafter see, is a far more important circumstance) with different sets of organic beings. But my tables further show that, in any limited country, the species which are most common, that is abound most in individuals, and the species which are most widely diffused within their own country (and this is a different consideration from wide range, and to a certain extent from commonness), often give rise to varieties sufficiently well-marked to have been recorded in botanical works. Hence it is the most flourishing, or, as they may be called, the dominant species,— those which range widely over the world, are the most diffused in their own country, and are the most numerous in individuals,—which oftenest produce well-marked varieties, or, as I consider them, incipient species. And this, perhaps, might have been anticipated; for, as varieties, in order to become in any degree permanent, necessarily have to struggle with the other inhabitants of the country, the species which are already dominant will be the most likely to yield offspring which, though in some slight degree modified, will still inherit those advantages that enabled their parents to become dominant over their compatriots.

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如果把任何植物志上记载的某地方生长的植物分作相等的两个群，把所有大属的植物放在一边，所有小属的植物放在另一边，则可发现大属那边很普通的、极分散的物种或优势物种略多。这也在预料之中，仅仅因为在任何地域内栖息着同属的许多物种，就表明该地有机、无机的条件里存在有利于该属的东西；结果，在大属里，即含有许多物种的属里，可望发现比例数目较多的优势物种。但是，可使这种结果暧昧不明的原因实在多，真奇怪我的表格甚至表明大属这一边略占多数。我在这里只提出两个暧昧的原因。淡水产喜盐的植物一般分布很广，且极分散，但这一点似乎和它们居住地方的性质有关，而和该物种所归的属之大小关系很少或没有关系。还有，体制低级的植物一般比高级的植物分散得更加广阔；而且这和属的大小也没有密切关联。体制低级的植物分布广的原因，将在“地理分布”一章讨论。

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If the plants inhabiting a country and described in any Flora be divided into two equal masses, all those in the larger genera being placed on one side, and all those in the smaller genera on the other side, a somewhat larger number of the very common and much diffused or dominant species will be found on the side of the larger genera. This, again, might have been anticipated; for the mere fact of many species of the same genus inhabiting any country, shows that there is something in the organic or inorganic conditions of that country favourable to the genus; and, consequently, we might have expected to have found in the larger genera, or those including many species, a large proportional number of dominant species. But so many causes tend to obscure this result, that I am surprised that my tables show even a small majority on the side of the larger genera. I will here allude to only two causes of obscurity. Fresh-water and salt-loving plants have generally very wide ranges and are much diffused, but this seems to be connected with the nature of the stations inhabited by them, and has little or no relation to the size of the genera to which the species belong. Again, plants low in the scale of organisation are generally much more widely diffused than plants higher in the scale; and here again there is no close relation to the size of the genera. The cause of lowly-organised plants ranging widely will be discussed in our chapter on geographical distribution.

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由于我把物种看作只是特性显著、定义明确的变种，所以预料各地大属的物种应比小属的物种更常出现变种；因为，无论哪里有许多密切近似物种（即同属的物种）形成，一般应有许多变种即初始物种正在形成。哪里有许多大树生长，哪里可望找到幼苗。哪里有属的许多物种因变异而形成，哪里的条件必有利于变异；因此，可望这些条件一般还会继续有利于变异。相反，我们如果把各个物种看作是特别创造出来的，就没有明显的理由来说明，为什么含有多数物种的类群比含有少数物种的类群会发生更多的变种。

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From looking at species as only strongly-marked and well-defined varieties, I was led to anticipate that the species of the larger genera in each country would oftener present varieties, than the species of the smaller genera; for wherever many closely related species (i.e. species of the same genus) have been formed, many varieties or incipient species ought, as a general rule, to be now forming. Where many large trees grow, we expect to find saplings. Where many species of a genus have been formed through variation, circumstances have been favourable for variation; and hence we might expect that the circumstances would generally be still favourable to variation. On the other hand, if we look at each species as a special act of creation, there is no apparent reason why more varieties should occur in a group having many species, than in one having few.

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为了测试这种预料的正确性，我把十二个地区的植物及两个地区的鞘翅类昆虫排列为差不多相等的两群，大属的物种排一边，小属的物种排另一边；结果毫无例外地证明了，大属一边比小属一边产生变种的物种比例更高。另外，产生任何变种的大属物种，一律比小属的物种所产生的变种平均更多。如果采用另一种分群方法，彻底排除表内只有一个到四个物种的最小属，这两个结果也一样。这些事实清楚地表明，物种仅是显著标记而永久的变种而已；无论哪里同属的物种大量形成，或者不妨说，哪里物种制造厂活动过，一般应该发现这些工厂仍在活动，特别是我们可以有充分的理由相信，新种的制造是一个缓慢的过程。如果把变种看作初始物种，上述这一点肯定属实；因为我的表格一般清楚地表明，无论哪里属的物种大量形成，这个属的物种产生的变种（即初始物种）就会在平均数以上。倒不是说所有大属现在变异都很大，因而都在增加物种数量，也不是说小属现在都不变异，不增加物种；否则我的学说就要受到灭顶之灾。地质学明白地告诉我们，小属随着时间的推移常常会大事增大；而大属常常已经达到顶点，而衰落消失。我们所要阐明的仅仅是，哪里有属的物种大量形成，一般说来就有许多物种还在形成；这可谓言之有理。

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To test the truth of this anticipation I have arranged the plants of twelve countries, and the coleopterous insects of two districts, into two nearly equal masses, the species of the larger genera on one side, and those of the smaller genera on the other side, and it has invariably proved to be the case that a larger proportion of the species on the side of the larger genera present varieties, than on the side of the smaller genera. Moreover, the species of the large genera which present any varieties, invariably present a larger average number of varieties than do the species of the small genera. Both these results follow when another division is made, and when all the smallest genera, with from only one to four species, are absolutely excluded from the tables. These facts are of plain signification on the view that species are only strongly marked and permanent varieties; for wherever many species of the same genus have been formed, or where, if we may use the expression, the manufactory of species has been active, we ought generally to find the manufactory still in action, more especially as we have every reason to believe the process of manufacturing new species to be a slow one. And this certainly is the case, if varieties be looked at as incipient species; for my tables clearly show as a general rule that, wherever many species of a genus have been formed, the species of that genus present a number of varieties, that is of incipient species, beyond the average. It is not that all large genera are now varying much, and are thus increasing in the number of their species, or that no small genera are now varying and increasing; for if this had been so, it would have been fatal to my theory; inasmuch as geology plainly tells us that small genera have in the lapse of time often increased greatly in size; and that large genera have often come to their maxima, declined, and disappeared. All that we want to show is, that where many species of a genus have been formed, on an average many are still forming; and this holds good.

20
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大属的物种和其中有记载的变种之间，有值得注意的其他关系。我们已经看到，辨别物种和显著变种并没有颠扑不破的标准；在存疑类型之间没有找到中间连锁的时候，学者就不得不依据它们之间的差异量来决定，用类推的方法来判断其差异量是否足够把一方或双方升到物种的等级。因此，差异量就成为解决两个类型究竟应该列为物种还是变种的极其重要的标准。弗里斯（Fries）曾就植物，韦斯特伍德（Westwood）曾就昆虫说明，大属里物种之间的差异量往往极小。我曾努力以平均数来测试这种情形，所得到的粗浅结果总是证实这种观点。我还询问过几位睿智的、经验丰富的观察者，他们三思之后也赞同这种意见。所以，在这方面，大属的物种比小属的物种更像变种。这种情形可换一种说法，也就是说，在大属里，超过平均数的变种即初始物种现在还在制造中，许多已经制造成的物种在某种程度上还是和变种相似，因为这些物种彼此的差异不及普通的差异量大。

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There are other relations between the species of large genera and their recorded varieties which deserve notice. We have seen that there is no infallible criterion by which to distinguish species and well-marked varieties; and in those cases in which intermediate links have not been found between doubtful forms, naturalists are compelled to come to a determination by the amount of difference between them, judging by analogy whether or not the amount suffices to raise one or both to the rank of species. Hence the amount of difference is one very important criterion in settling whether two forms should be ranked as species or varieties. Now Fries has remarked in regard to plants, and Westwood in regard to insects, that in large genera the amount of difference between the species is often exceedingly small. I have endeavoured to test this numerically by averages, and, as far as my imperfect results go, they always confirm the view. I have also consulted some sagacious and most experienced observers, and, after deliberation, they concur in this view. In this respect, therefore, the species of the larger genera resemble varieties, more than do the species of the smaller genera. Or the case may be put in another way, and it may be said, that in the larger genera, in which a number of varieties or incipient species greater than the average are now manufacturing, many of the species already manufactured still to a certain extent resemble varieties, for they differ from each other by a less than usual amount of difference.

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而且，大属内物种的相互关系，同任何一个物种的变种是相似的。没有一位学者宣称，属内的全部物种在彼此区别上是相等的；一般地可以把它们区分为亚属、组（sections）或更小的类群。弗里斯说得好，小群物种一般就像卫星环绕在其他物种的周围。因此，所谓变种，还不是一群类型，它们的彼此关系不均等，环绕在某些类型——即环绕在其亲种的周围？变种和物种之间无疑存在着一个极重要的不同点，即变种彼此之间的差异量，或与其亲种的差异量，比起同属的物种之间要小得多。但是，当我们讨论到我称为“性状的分歧”的原则时，将会看到如何解释这一点，变种之间的小差异将倾向于增大为物种之间的大差异。

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Moreover, the species of the large genera are related to each other, in the same manner as the varieties of any one species are related to each other. No naturalist pretends that all the species of a genus are equally distinct from each other; they may generally be divided into sub-genera, or sections, or lesser groups. As Fries has well remarked, little groups of species are generally clustered like satellites around certain other species. And what are varieties but groups of forms, unequally related to each other, and clustered round certain forms—that is, round their parent-species? Undoubtedly there is one most important point of difference between varieties and species; namely, that the amount of difference between varieties, when compared with each other or with their parent-species, is much less than that between the species of the same genus. But when we come to discuss the principle, as I call it, of Divergence of Character, we shall see how this may be explained, and how the lesser differences between varieties will tend to increase into the greater differences between species.

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我看还有一点值得注意。变种的分布范围一般都十分有限；这话确是不讲自明的，如果发现一个变种比它的假定亲种有更广阔的分布范围，那就应该把名称倒转过来了。但是也有理由相信，同其他物种密切相似的并且类似变种的物种，常常有极有限的分布范围。例如，沃森先生曾把精选的《伦敦植物名录》（第四版）列为物种的63种植物指给我看，但他认为它们同其他物种太相似，所以价值存疑。根据沃森先生所做的英国区划，这63个所谓物种的分布范围平均为6.9区。在同一《名录》里，记载着53个公认的变种，分布范围为7.7区；而这些变种所属的物种的分布范围为14.3区。所以公认的变种和密切相似的类型具有几乎一样的有限平均分布范围，后者就是沃森先生指出的所谓存疑物种，但它们几乎普遍地被英国学者们列为货真价实的物种了。

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There is one other point which seems to me worth notice. Varieties generally have much restricted ranges: this statement is indeed scarcely more than a truism, for if a variety were found to have a wider range than that of its supposed parent-species, their denominations ought to be reversed. But there is also reason to believe, that those species which are very closely allied to other species, and in so far resemble varieties, often have much restricted ranges. For instance, Mr. H. C. Watson has marked for me in the well-sifted London Catalogue of plants (4th edition) 63 plants which are therein ranked as species, but which he considers as so closely allied to other species as to be of doubtful value: these 63 reputed species range on an average over 6.9 of the provinces into which Mr. Watson has divided Great Britain. Now, in this same catalogue, 53 acknowledged varieties are recorded, and these range over 7.7 provinces; whereas, the species to which these varieties belong range over 14.3 provinces. So that the acknowledged varieties have very nearly the same restricted average range, as have those very closely allied forms, marked for me by Mr. Watson as doubtful species, but which are almost universally ranked by British botanists as good and true species.

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最后，变种具有与物种相同的一般性状，无法和物种区别——除非，第一，发现了中间的连锁类型，而这种连锁的出现不能影响其所连接的类型的实际性状；第二，两者之间具有一定的差异量，因为两个类型如果差异很小，一般列为变种，虽然并没有发现中间的连锁类型，但是给予两个类型物种地位所需要的差异量，却是不确定的。在任何地方，含有超过平均数的物种的属，其中的物种也有超过平均数的变种。在大属里，物种易于密切但不均等地相互近似，环绕某些物种形成小群。与其他物种密切近似的物种显然具有有限的分布范围。在上述这些方面，大属的物种极类似于变种。如果物种曾经作为变种而生存过，并且是由变种产生的，我们便可以明白这种类似性；然而，如果各物种是独立创造的，这种类似性就完全不能解释了。

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Finally, then, varieties have the same general characters as species, for they cannot be distinguished from species,—except, firstly, by the discovery of intermediate linking forms, and the occurrence of such links cannot affect the actual characters of the forms which they connect; and except, secondly, by a certain amount of difference, for two forms, if differing very little, are generally ranked as varieties, notwithstanding that intermediate linking forms have not been discovered; but the amount of difference considered necessary to give to two forms the rank of species is quite indefinite. In genera having more than the average number of species in any country, the species of these genera have more than the average number of varieties. In large genera the species are apt to be closely, but unequally, allied together, forming little clusters round certain species. Species very closely allied to other species apparently have restricted ranges. In all these several respects the species of large genera present a strong analogy with varieties. And we can clearly understand these analogies, if species have once existed as varieties, and have thus originated: whereas, these analogies are utterly inexplicable if each species has been independently created.

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我们还看到，大属中越是繁盛的优势物种，平均变种越多；而我们以后将看到，变种倾向于变成新物种。因此大属倾向于变得更大；自然界中，现在占优势的生物类型由于留下了许多变异了的优势后代，倾向于更加占有优势。但是经过以后要说明的步骤，大属也有分裂为小属的倾向。这样，全世界的生物类型就在类群之下又分为类群了。

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We have, also, seen that it is the most flourishing and dominant species of the larger genera which on an average vary most; and varieties, as we shall hereafter see, tend to become converted into new and distinct species. The larger genera thus tend to become larger; and throughout nature the forms of life which are now dominant tend to become still more dominant by leaving many modified and dominant descendants. But by steps hereafter to be explained, the larger genera also tend to break up into smaller genera. And thus, the forms of life throughout the universe become divided into groups subordinate to groups.

序号 英文/音标 中文解释 更多操作

diffuse

[dɪ'fjuːz]

vt.扩散

genus

['dʒiːnəs]

n.【生物学】属;类;种;型

unequal

[ʌn'iːkwəl]

adj.不相等的;不平等的;不胜任的

naturalist

['nætʃrəlɪst]

n.自然主义者;博物学者

descent

[dɪ'sent]

n.下降;下坡;家世;血统;侵袭;衰落;继承

deviation

[ˌdiːvi'eɪʃn]

n.偏离;出轨;背弃

propagate

['prɒpəɡeɪt]

v.繁殖;增殖;传播;传送

modification

[ˌmɒdɪfɪ'keɪʃn]

n.修改;修正;修饰

Baltic

['bɔːltɪk]

adj.波罗的海的;波罗的语的

offspring

['ɒfsprɪŋ]

n.后代;子孙;产物

inhabit

[ɪn'hæbɪt]

v.居住于;占据;栖息

locality

[ləʊ'kæləti]

n.地区;位置;地点;方位

casting

['kɑːstɪŋ]

n.铸造

mould

[məʊld]

n.发霉;模具

domesticate

[də'mestɪkeɪt]

vt.驯养;使专注于家务;教化

unimportant

[ˌʌnɪm'pɔːtnt]

adj.不重要的

physiological

[ˌfɪziə'lɒdʒɪkl]

adj.生理的;生理学的

laborious

[lə'bɔːriəs]

adj.艰苦的;费劲的

specimen

['spesɪmən]

n.标本;样本

irregular

[ɪ'reɡjələ(r)]

adj.不规则的;不整齐的;不合法的;不合规矩的

larva

['lɑːvə]

n.幼虫;幼体

perplex

[pə'pleks]

v.使困惑;使糊涂;使复杂化

hybrid

['haɪbrɪd]

n.混合物;杂种;混血儿

competent

['kɒmpɪtənt]

adj.有能力的;足够的;胜任的

uncommon

[ʌn'kɒmən]

adj.不寻常的;不常见的;极度的

Flora

['flɔːrə]

n.植物;群落(大写)Flora：【罗神】花神弗洛拉; 弗洛拉(女名).

botanist

['bɒtənɪst]

n.植物学家

whereas

[ˌweər'æz]

conj.然而;鉴于

locomotive

[ˌləʊkə'məʊtɪv]

n.火车头

eminent

['emɪnənt]

adj.著名的;卓越的

undoubted

[ʌn'daʊtɪd]

adj.无疑的

mainland

['meɪnlænd]

n.大陆;本土

islet

['aɪlət]

n.小岛

entomologist

[ˌentə'mɒlədʒɪst]

n.昆虫学家

zoologist

[zəʊ'ɒlədʒɪst]

n.动物学家

ample

['æmpl]

adj.丰富的;宽敞的;充足的

odor

['əʊdə]

n.气味;名声;气息

ascend

[ə'send]

v.上升;攀登

botanical

[bə'tænɪkl]

adj.植物学的;植物的

allude

[ə'luːd]

v.暗示;暗指

continual

[kən'tɪnjuəl]

adj.不断的;频繁的;连续的

climax

['klaɪmæks]

n.高潮;极点;层进法;【生】顶极群落;巅峰，最高峰

lesser

['lesə(r)]

adj.较少的;较小的;次要的

incipient

[ɪn'sɪpiənt]

adj.起初的;初期的

extinct

[ɪk'stɪŋkt]

adj.灭绝的;熄灭的;消亡的

arbitrarily

[ˌɑːbɪ'trɛərɪlɪ]

adv.任意地;武断地;专横地

fluctuate

['flʌktʃueɪt]

vi.波动;动摇;起伏

tabulate

['tæbjuleɪt]

v.制成表;使成平面

proportional

[prə'pɔːʃənl]

adj.成比例的;相称的

manuscript

['mænjuskrɪpt]

n.手稿;原稿

compatriot

[kəm'pætriət]

n.同国人;同胞;同事

inorganic

[ˌɪnɔː'ɡænɪk]

adj.无机的;非自然生长的

sapling

['sæplɪŋ]

n.树苗;小树;年轻人

anticipation

[ænˌtɪsɪ'peɪʃn]

n.预期;预料;期待，希望

invariably

[ɪn'veəriəbli]

adv.不变地;总是;一贯地

manufacture

[ˌmænju'fæktʃə(r)]

v.(手工)制造

geology

[dʒi'ɒlədʒi]

n.地质学;(某地区的)地质情况;地质学的著作

lapse

[læps]

n.过失;流逝;间隔;堕落;失效

criterion

[kraɪ'tɪəriən]

n.标准;准则

suffice

[sə'faɪs]

vi.足够;使满足

fry

[fraɪ]

v.油煎;油炸

numerical

[njuː'merɪkl]

adj.数字的;用数字表示的

imperfect

[ɪm'pɜːfɪkt]

adj.不完美的;有缺点的;未完善的

scarcely

['skeəsli]

adv.几乎不;简直不;刚刚;决不

repute

[rɪ'pjuːt]

n.名声;名气;声望

occurrence

[ə'kʌrəns]

n.发生

indefinite

[ɪn'defɪnət]

adj.模糊的;不确定的;无限期的

utterly

['ʌtəli:]

adv.完全;全然;绝对

independently

[ˌɪndɪ'pendəntli]

adv.独立地;自立地

descendant

[dɪ'sendənt]

n.后裔;子孙;后代

hereafter

[ˌhɪər'ɑːftə(r)]

adv.此后;将来;来世

genus

['dʒiːnəs]

n.【生物学】属;类;种;型

subordinate

[sə'bɔːdɪnət]

adj.下级的;次要的

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