ON SOMATIC SEX-CHARACTERS 83 



on the head, a white neck-ring, much claret colour 

 on the breast, and some feathers indistinguishable 

 from those of the male, and also the male sex feathers 

 on the tail. Goodale concludes that the female 

 owes her normal colour to the ovaries or something 

 associated with them which suppresses the male 

 characters and ensures the development of her own 

 type. He considers it is quite as conceivable that 

 selection should operate to pick out inconspicuously 

 coloured females as that selection of brilliantly 

 coloured males should bring about an addition to the 

 female type. But as pointed out above, selection 

 cannot explain the dimorphism in either case. 



It may be mentioned here that owing to the fact 

 that the single (left) ovary in birds is very closely 

 attached to the peritoneum immediately covering 

 the great post-caval vein, it is generally impossible 

 to remove the whole of the ovary without cutting 

 or tearing the wall of the vein and so causing 

 fatal hemorrhage. The above results observed by 

 Goodale are therefore all the more remarkable, and it 

 may be assumed that he removed at any rate nearly 

 all the ovary. 



The research of Seligmann and Shattock ^ begins 

 with a comparison between the stages of the develop- 

 ment of the nuptial plumage and the stages of 

 spermatogenesis. In the young pheasant the male 

 plumage is fully developed in the autumn of its first 

 year, but no pairing occurs and no sexual instinct is 

 exhibited till the following spring. The wild duck 

 pairs in autumn or early winter, after the assumption 



^ * Relation between Seasonal Assumption of the EoIipHo Plumago in 

 the Mallard {Anas boscas) and the Functions of the Testicle.' Froc. Zool. 

 Soc, 1914. 



