280 Mr Barrett-Hamilton, Secondary Sexual Characters 



in the case of many of the more intelligent animals such as the 

 Mammalia. Again, among Birds, the sexes of the Corvidae, 

 wherein we should surely have expected to find the greatest 

 possible enjoyment of aesthetic display, are often alike. On the 

 other hypothesis, if it be true that the males are inherently more 

 vigorous than their females, how are we to account for the fact 

 that in some whole families such as the diurnal Birds of Prey 

 (Accipitres) the females are the larger ? In the case of some other 

 Birds — as the Hemipodes (Turnix) and the Phalaropes (Phala- 

 ropus) — and some few others it is the female and not the male 

 which assumes the brightest breeding plumage, which exceptions 

 to the general rule are usually explained by the fact, more or less 

 ascertained, that there is here an exchange of function, the male 

 performing the duty of incubation. Yet that the nuptial weapons 

 or ornaments are mainly dependent on the condition of the 

 sexual organs, has been asserted from the days of John Hunter. 

 Since his time the question has been examined by many in- 

 vestigators, and a considerable number of cases have been recorded, 

 principally amongst Birds, in which the alleged intimate relation 

 between the condition of the generative organs and the external 

 sexual characters has been usually affirmed, but sometimes ques- 

 tioned 1 and even denied. 



But what seems to me to throw most doubt of all upon the 

 aesthetic theory as the guiding principle and upon that which 

 relies upon the greater vigour of the male as the primary cause 

 is the fact that in the case of many Birds, and those apparently 

 of stupid species which we cannot suppose to be capable of 

 appreciating differences of colour-tints, both sexes share in nuptial 

 changes which may be very striking. Such is the case, for 

 instance, amongst many sea birds. The crest and white side- 

 tufts of the Shags (Phalacrocorax) and the wonderful mandibular 

 excrescences and facial plumes of the little Auks and Puffins 

 {Fratercula, Lunda, Simorhynchus and others) are temporarily 

 assumed by both sexes. 



The wide-ranging nature of these phenomena, and their 

 prevalence not only among vertebrates but among invertebrates, 

 as, for instance, to quote only familiar instances, amongst the 

 Spiders 2 of the family Attidae and many Linyphiidae, or amongst 

 the Lepidoptera, suggests that there must be some wide-spread and 

 fundamental causes to which all owe their origin, some primary 

 state of things from which they all started, and which, once found, 



1 See a paper by Mr J. H. Gurney, Junior, on " Male Plumage in Female Birds," 

 Ibis, 1888, p. 226, also Zoologist, 1894, p. 15 : also a paper by the same author on 

 a female Kedstart which assumed the plumage of a male, in Trans. Nonvich Nat. 

 iv. p. 182. 



2 A piece of information for which I am indebted to my friend Mr E. I. Pocock. 



