246 T. H. MORGAN. 



feathering characteristics of the male of her race (Goodale). 

 Elsewhere I have discussed how these effects are brought about 

 whether the same kinds of secreting cells are present. in the 

 ovary and in the testes of the hen-feathered males. This ques- 

 tion is being further studied at present and need not be consid- 

 ered here. 



The comb and wattles are the most remarkable secondary 

 sexual characters of the cock. Their condition is a close index 

 of the condition o'f the gonad. In fact, after castration their size 

 and the amount of blood present in them indicates how far 

 the gonad has been removed. Even a very small piece of the 

 testis suffices to cause them to grow to their full size. This is 

 well shown in the pictures of two of the Campines described 

 above, in which the comb became reduced shortly after the opera- 

 tion, and then slowly grew almost to its full size in the course of 

 the following months. Its paleness showed, however, that the 

 testes were not normal in size, and this was confirmed by autopsy. 

 When the birds were killed a small piece of the testis was found. 

 In the hen, too, it appears that the ovary has an inhibitory influ- 

 ence on the comb and wattles; for, as Goodale has shown they 

 become larger in the ovariotomized birds. Since the testes of 

 the normal full-grown cock-feathered bird seem deficient, or 

 lacking in luteal cells (Boring and Morgan) it may appear that 

 these cells do not produce the endocrine secretion that affects 

 the comb, although if it can be shown that they do not completely 

 disappear even in adult cock-feathered birds it may be that a 

 much smaller amount of this secretion than is essential for sup- 

 pressing the cock-feathering suffices to cause the enlargement of 

 the comb and wattles. But if, as is said to be the case, the luteal 

 cells disappear entirely in the adult cock-feathered bird, then 

 there must be some other element in the testis that maintains the 

 comb and the wattles at their maximum size. Here again is a 

 further field for investigation. 



BIBLIOGRAPHY. 

 Boring, Alice M. 



'12 The Interstitial Cells and the Supposed Internal Secretion of the 

 Chicken Testis. BIOL. BULL., XXIII. 



