NATURE 



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THURSDAY, OCTOBER 6, 1892. 



NATURAL SELECTION AND ALTERNATIVE 

 HYPO THESES. 



Animal Coloration : an Account of the Principal Facts 

 and Theories relatitig to the Colours and Markins;s of 

 Animals. By F. E. Beddard, M.A., F.R.S. (Swan 

 Sonnenschein & Co.) 



THE theory of natural selection has been pre-eminent 

 for over thirty years as the most generally accepted 

 explanation of organic evolution. It has, and has had 

 throughout, many critics ; but its position is strengthened 

 by the fact that these critics invariably accept the principle 

 as accounting for something, while most of them make it 

 clear that they reject all other proposed substitutes, ex- 

 cept those for which they are individually responsible. 

 Sometimes the attempt to formulate an alternative hypo- 

 thesis, or to apply it to the facts of nature, breaks down 

 as soon as it is undertaken. A curious instance of this is 

 to be found in Semper's "Animal Life,' which begins 

 with very large anticipations : — all the " popular cant " 

 of the Darwinian is to be " put out of court as useless " ; 

 a selective explanation can never be a real one, but for the 

 latter we are to consult the subsequent pages. But as 

 case after case is examined, the author is constrained to 

 admit that his real explanation is not forthcoming, and 

 that, although he never will think much of selection, it is 

 the only cause he has to offer. Semper would appear to 

 have written his preface before he considered the 

 materials from which he proposed to write his book. 



Mr. Beddard's work does not open in this ambitious 

 manner, but he is far bolder in offering alternatives to 

 natural selection, and in applying them. Further con- 

 sideration would probably have brought him to Semper's 

 admission, at least as regards many of his suggestions. 

 Indeed, the number of these suggestions, and the confi- 

 dence with which they are brought forward, are clearly 

 due to haste and want of sufficient reflection, which also 

 leave their mark upon the scheme of the volume and the | 

 number of contradictory statements to be found in it. i 

 Nor is this to be wondered at when the amount and I 

 variety of work which the author accomplishes is borne 

 in mind. But the result will be to confuse the beginner ' 

 and the untrained student. Principles which are sup- 

 posed to be refuted in one part, are subsequently intro- 

 duced with considerable enthusiasm as the heads of the 

 main sections of the work, and are later on again treated 

 with scant courtesy. In fact some readers will rightly infer 

 that the author is a profound sceptic as to the value of 

 the scheme he nevertheless adopts. Others may perhaps 

 be led to suppose, by the arrangement of the book, that 

 the author is sceptical of his own scepticism. Even the 

 very fairness of the author in giving the arguments in | 

 favour of views he rejects, will be, such is the system 

 pursued, a cause of confusion to a reader. These sources 

 of difficulty are not only apparent in the general scheme ; 

 particular explanations are disputed in one part, and 

 adopted a little further on without a word of explanation. 



The chief value of the book lies in the fact that it is 

 NO. I 197. VOL. 46] 



straightforward, and speaks out on points of great diffi- 

 culty and dispute. Arguments of which echoes have been 

 already heard, perhaps, in the report of some conversa- 

 tion which is supposed to have taken place, or which 

 have been crudely stated in the publications of unknown 

 writers, are here met with in a form in which they can be 

 dealt with. For thus stating the opinions which are 

 vaguely supposed to be held, perhaps vaguely held, by 

 others, every Darwinian owes a debt of gratitude to the 

 author. 



The main aim and purpose of the book would appear 

 to be a criticism of natural selection as applied to the 

 explanation of the colours of animals, and the proposal of 

 alternative explanations. 



Some of the difficulties which the author finds in the 

 theory of natural selection appear to follow from his 

 conception of the process itself. Thus, on p. 12, he 

 speaks of polymorphic species appearing in two or more 

 well-marked forms, and of those extreme cases of varia- 

 tion known to entomologists as "varieties," and con- 

 cludes, " In fact, if colouring were really constant for a 

 given species, there would be no chance for natural 

 selection"; thus implying that natural selection depends 

 upon such pronounced divergences, instead of upon those 

 minute differences which distinguish the individuals of 

 every species. He then continues, " Supposing that a 

 marked variety occurs in a wild species, there is, first 

 of all, a considerable chance against its reaching matu- 

 rity ; secondly, there is a considerable chance against its 

 finding a mate ; thirdly, the hereditary influences on both 

 sides are against the perpetuation of the variety. These 

 appear to be more potent causes of the comparative fixity of 

 colours in wild animals than the unfitness of the varieties to 

 live." It has already been pointed out that the " marked 

 variety " is of little importance for natural selection as 

 compared with the individual difference. But if the ob- 

 jections urged were valid there would appear to be little 

 chance of a " marked variety " existing in any numbers 

 and persisting from generation to generation, side by side 

 with the normal form : and yet numbers do persist. As to 

 the first of the alleged objections, the chances are against 

 every individual, but not equally so, if there be anything 

 in natural selection. So far from this objection being 

 valid, it is but the expression of a fact upon which 

 natural selection rests, the fact that many more indi- 

 viduals of every species are born into the world than can 

 by any possibility survive. Were this not so all selection 

 would cease. The second difficulty certainly does not 

 apply to minute individual differences which occur in 

 vast numbers. To take the simplest case, let us suppose 

 that the individuals of a species are divided, as regards 

 any character, into two equal groups— the one above, 

 the other below the mean. It is clear that each indi- 

 vidual would stand as good a chance of mating within 

 the limits of its own group as within those of the other. 

 The third objection does not appear to me to hold in the 

 case of "marked varieties" any more than with indi- 

 vidual differences. The total hereditary influence of the 

 varying side, allowing even considerable force for atavism, 

 is certainly in favour of the variation. Furthermore, 

 experience shows us that among the offspring will be 

 some that vary even further than their parent. Those 



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