December 27, 1900] 



NA TURE 



199 



the author discusses, in this chapter, the origin of antlers, 

 horns and tusks, which, being used for fighting, have, 

 according to his views, been developed by pushes and 

 stimulating shocks. The cheek prominences of the male 

 mandrill are considered to have been produced by a 

 similar process, and their furrows and colour are regarded 

 as "inherited swellings and scars" (p. 58). The case 

 for Lamarckism, as based on a study of antlers, is worked 

 out at great length also in this chapter, this being a sub- 

 ject to which Mr. Cunningham has devoted special atten- 

 tion. The tusk-like development of the upper canines 

 of the male musk deer is explained in these words : 



"The enlargement of a tooth is as natural a con- 

 sequence of excessive use as is that of an antler, the 

 pressure stimulating the papilla or pulp from which the 

 tooth is developed " (p. 96). 



The author adds, however, that the evolution of the 

 musk gland of the male " is more difificult to explain." 



Those who are familiar with Darwin's weighty body 

 of evidence in favour of sexual selection derived from 

 his studies of the secondary sexual characters of birds 

 will turn with interest to the discussion of this subject 

 in the second chapter of the present work. The exces- 

 sive development of male plumage is, according to the 

 author, the result of use— /.^. to erection by muscular 

 action during display. But the most striking sexual 

 differences among birds are not only due to development 

 of plumage, but also to colour and pattern, and just on 

 this point Mr. Cunningham's application of Lamarckism 

 becomes most unsatisfactory : — 



" With regard to the coloration and markings of special 

 plumage I have little to say. I regard them as due 

 partly to the same excessive growth as that which in- 

 creases the size of the feather, partly to the universal 

 regularity and symmetrical repetition of marks, due to 

 the rhythmical nature of growth processes, and partly 

 perhaps to the action of the light from particular sur- 

 roundings" (p. 109). 



From this point of view, it is interesting to see how 

 the author deals with the ocelli of Polyplectron (p. 114). 

 Darwin, as is well known, attributed the dull ocelli of 

 the female to partial transference of the male characters. 

 Mr. Cunningham inverts this explanation, and suggests 

 that the present condition of the female represents the 

 original condition of the male. In other words, the 

 ocelli of the male as at present seen are the female 

 ocelli developed and enhanced by " use inheritance." 

 The writer of this notice fails to see wherein this ex- 

 planation offers any advantage. The duller ocelli of the 

 female have, on this view, still to be accounted for. What 

 direct action or external stimulus or impact can be con- 

 ceived which is capable of producing regular patterns ? 

 The " action of light from particular surroundings " (even 

 if we admitted such action) could not produce an ocellus, 

 and if the " rhythmical nature of growth processes " is 

 considered a sufficient explanation, this and all similar 

 cases are at once removed from the discussion, and have 

 no more to do with the author's Lamarckism than with 

 the older Darwinism. 



The whole treatment of colour and pattern throughout 



the work leaves no doubt that the author proposes to 



ring these characters within the domain of his amended 



amarckism. Among Amphibia, for example, the more 



NO. 1626, VOL. 63] 



vivid colouring of the male Molge aspeia is attributed to 

 the greater sexual excitement of the male, which causes, 

 " through nervous stimulation, more active production of 

 pigment in the skin" (p. 175). Among fish — a class to 

 which Mr. Cunningham has paid special attention — the 

 same explanation is offered again and again to account 

 for the brighter colours of males. In those exceptional 

 cases where, as in Solenostoma (p. 227), the female is the 

 more brilliantly marked and coloured, the author is 

 obliged to reverse the nervous excitement of the sexes. 

 Perhaps the most instructive case dealt with under this 

 division is that of the male dragonet, Callionymus lyra, 

 because it is discussed at great length (pp. 199 — 214), and 

 may be taken as a typical example of the author's treat- 

 ment of the problem of colour as a secondary sexual 

 character. The habits of the fish have, moreover, been 

 most thoroughly observed and recorded by Mr. Holt at 

 the Plymouth Marine Station. In summing up this case 

 Mr. Cunningham concludes, as before, that the increased 

 sexual excitement of the male at the breeding period 

 causes, through nervous stimulation, an increased deposi- 

 tion of guanine and pigment in the skin. 



"That the marked excitement of the male dragonet's 

 brain should cause increased nervous stimulation of the 

 skin is not an extravagant supposition, and it is definitely 

 supported by the fact that the blue bands, if not the 

 yellow, are flashed out in more intense brilliance as the 

 fins are raised in his amatory rushes. When the question 

 is regarded physiologically, instead of merely from the 

 selectionist's point of view, the significance of such 

 reasoning as I have used cannot be ignored." 



In this paragraph Mr. Cunningham takes up a position 

 that is very frequently assumed by opponents of the 

 selection theory, and from which the writer of this notice 

 desires to take this opportunity of again expressing his 

 dissent. The fact that the blue bands are flashed out as 

 the fins are raised is surely an optical effect. I can hardly 

 imagine that even the Lamarckian zeal of the author 

 would lead him to desire that his readers should suppose 

 that the " amatory rush " of the male caused an immediate 

 and suddenly increased secretion of guanine ! But apart 

 from this, supposing we admit that he has discovered the 

 true physiological explanation of the colour — and that 

 given on p. 211 may be perfectly correct — wherein does 

 this favour the Lamarckian and discredit the Darwinian 

 explanation? It appears to be constantly assumed by 

 anti-Darwinians that because they have found the phy- 

 siological and histological mechanism of a colour they 

 have thereby disposed of selection. We say that selec- 

 tion is capable of acting upon all characters, external 

 and internal — whatever their physiological origin ; and, 

 in this particular case, if the male fish were capable at 

 the breeding period of secreting guanine to such an 

 extent and in such an arrangement as to produce a 

 visible blue colour, we should say that there is here a 

 character which is quite as capable of being enhanced 

 and developed by sexual selection as is any other 

 character of biological value to the species by natural 

 selection. 



In association with the hypothesis that colour is the 

 result of increased deposition of pigment due to sexual 

 excitement, it may be pertinent here to raise the question 

 why, on Lamarckian principles, the increased secretory 



