240 



T. H. MORGAN. 



explanation of the appearance of cock-feathers. Something had 

 kept back the normal growth of the testes, and their small size 

 was insufficient to entirely suppress the cock-feathering that the 

 genetic complex of the bird called for. The testes were sec- 

 tioned and studied by Dr. Jose Nonidez who furnishes the fol- 

 lowing report. ' The luteal cells are very abundant in the spaces 



FIG. 7. Feathers of Fig. 6, a, b, c, d, before castration June 17, 1919 ; a'-d 1 .- 

 at the time of castration Sept. 13 ; and a~-d' 2 , March 2, 1920. 



between the tubules especially in the periphery of the testes. In 

 the clusters of luteal cells, however, most of them appear to be 

 undergoing degeneration, for, the nuclei are a good deal shrunken 

 and the protoplasm has lost its round vacuoles, and is changed 

 into a clear space around the nucleus, hence the clear appearance 

 of the clusters made up of such degenerating cells. Extreme 

 cases of degeneration are found here and there, the nucleus hav- 

 ing lost all its structure. On the other hand, normal or nearly 

 normal cells are not rare; they are found in clusters containing 

 degenerated cells ; hence the appearance of the latter can not be 

 attributed to defective preservation." 



