242 



T. H. MORGAN. 



normal spermatogenesis had started and all the stages, from the 

 spermatogonia to mature spermatozoa, could be observed in the 

 slides. The spermatozoa finally degenerate and this is probably 

 due to the lack of an outlet in the organ. New tubules are aris- 

 ing near the surface of the section. The clusters of luteal cells, 

 however, have apparently disappeared, their place being taken 

 by the ordinary connective tissue and an enormous number of 

 small lymphocytes which are arising in the intertubular tissue at 

 this time. Some of these small lymphocytes become transformed 

 into large wandering cells which usually occur in the testis of 

 both hen- and cock-feathered birds. The disappearance of the 



! ) 



FIG. 9. Cock-feathered, normal cock and hen, from Wright's " Xew Book of 



Poultry." 



luteal cells may be accounted for by the failure of this tissue to 

 regenerate owing to its more or less abnormal condition at the 

 time of castration. If some of the cells found in the sections 

 are really luteal cells their numbers are probably too small to 

 induce any change in the characteristics of the plumage. The 

 relatively large size of the comb in the ' larger ' bird, on the 

 other hand, may be due, even in the case in which a very small 



