120 ORTHOGENETIC EVOLUTION IN PIGEONS. 



regions are marked by curved lines; fifthly, that the pattern changes, and the direction of 

 the lines, or spots, at the head, neck, and every joint of the limbs; and lastly, that the tips 

 of the ears, nose, tail, and feet, and the eye are emphasized in colour. In spotted annuals 

 the greatest length of the spot is generally in the direction of the largest development of 

 the skeleton. 



"This structural decoration is well seen in many insects," says Wallace. 10 In 

 caterpillars, this authority notes that similar spots and markings are repeated in 

 each segment, except where modified for some form of protection. In butterflies, 

 the spots and bands usually have reference to the form of the wing and the arrange- 

 ment of the nervures; and there is much evidence to show that the primitive mark- 

 ings are always spots in the cells, or between the nervures, or at the junctions, the 

 extension and the coalescence of these spots forming borders, bands, or blotches, 

 which have become modified in infinitely varied ways for protection, warning, or 

 recognition. Even in birds the distribution of colors and markings follows gener- 

 ally the same law. 11 



Sexual Dimorphism in Color. 



The following cases, among the several that might be instanced, indicate not 

 only that sex dimorphism in color depends upon the generative organs, but to me 

 they yield additional evidence that the male and female have potentially the same 

 characters. Usually the female lags behind, but sometimes the male lags. 12 



The first two instances are cited from Beddard : 13 



Prof. Max Weber, of Amsterdam, 14 has examined a chaffinch, in which the left side 

 of the body has the coloration of a hen bird, the right that of a cock, which are sharply 

 marked off from each other in the middle line. An examination of the viscera showed that 

 the bird was a hermaphrodite, with a well-developed ovary on that side of the body which 

 was clad with the plumage of the female, and a male gland on the opposite side. The same 

 kind of hermaphroditism has been noticed in other birds. In cases where a female bird 

 has assumed the plumage of the cock, it has been found that the ovary was diseased or 

 atrophied. 15 



The second instance which I shall bring forward is that of a moth — the common oak 

 eggar. Dr. Berthau 16 has figured and described a hermaphrodite specimen of this insect 

 in which the wings of one side of the body showed the coloration, form, and size of those 

 of a male, while the opposite couple of wings had the coloration of the female, and were, 

 as in the female moth, larger than the wings coloured after the male pattern. On a 

 dissection, the insect proved to be not hermaphrodite, like the chaffinch, but a female 

 with degenerate organs, some of the parts typically present being absent. It can not, 

 therefore, be called a hermaphrodite; it should be remarked that the ovary was more 

 degenerate upon the side of the body on which the wings were those of a male than upon 

 the other. 



10 Darwinism, Macmillan, London, 18S9, page 289. 



11 Reference to Eiiner's theory has several times been made in various chapters of this volume, and convincing 

 evidence for an antero-posterior law of the development of pattern — the opposite of Eimer's contention -has been 

 presented. It seems hardly advisable, therefore, to present here the rather lengthy critique of Eimer's work which 

 was written by the author at apparently disconnected intervals — 1899 to 1903. — Ed. 



12 See Darwin's Descent of Man, II, pages 191-199. 

 " Animal Coloration. 



» Zool. Anzeiger, 1890, page 508. 



16 See Mr. Bland Sutton's An Introduction to Pathology, for further instances. Also, .1. II. Gurney (jun.), Ibis, 

 1888, page 226. 



16 Arch. f. Naturgeschichte, lv, page 75. 



