Sept., 1892. colours and coloration in animals. 
205 
chaffinch, in which the left side of the body had the colora¬ 
tion of a hen bird, the right that of a cock, the colours being 
sharply marked off from each other in the middle line: 
the bird was a hermaphrodite, having a well-developed ovary 
on the left and a male gland on the right side of the body. 
According to our author, “ there is a fundamental difference 
between males and females, based upon the actual difference 
of sex, which generally finds an expression in outward 
unlikeness. These superficial differences may also be partly 
due to the different mode of life led by the two sexes. We 
meet with them in animals which cannot be moved by any 
choice or aesthetic preference ; but it is also true that they 
are most highly developed in the higher animals, where such 
choice is at least conceivable ; the mammal, however, forms a 
very important exception to this statement. Butterflies and 
birds show the most marked sexual dimorphism in colour ; 
and it is precisely in these two groups that there is the 
greatest opportunity for colour development, owing to the 
structure of their feathers and scales respectively. Colour 
differences become necessarily exaggerated in these animals, 
through mere multiplication of details. Nevertheless, it is 
quite possible that sexual selection may have played a 
subordinate part in the production of sexual coloration, and 
we may also allow some force to Stolzmann’s suggestions.” 
It will readily be gathered from the account which we 
have given that Mr. Beddard’s book is most suggestive, and a 
distinct addition to the literature of colours and coloration in 
animals. It is full of facts and ideas bearing on the subject, 
a few only of which we have been able to mention. These 
facts—some well, others little, known—are discussed by the 
author from all points of view. It is clear that he does not 
believe in the efficacy of the usually received theories to 
explain many of the cases which he adduces; but his 
criticisms, while to the point, are always temperate, his 
general treatment of the subject being characterised as much 
by its fairness as its acumen. We feel sure that the book will 
prove of great interest to general and scientific readers alike. 
One improvement should be made in a future edition—a 
fuller index ought to be given ; the existing one, while satis¬ 
factory as far as the names of the animals mentioned in the 
book are concerned, is utterly inadequate in regard to subjects, 
which are only referred to in the table of contents. It would 
be a very great convenience, and add undoubtedly to the value 
of the book, were all the references to such important subjects 
as “ vision,” “ pigment,” and a score of others, collected 
in the index. 
The letter-press is beautifully printed ; the illustrations, 
