TESTES OF GUINEA-CHICKEN HYBRIDS 47 



certain favorable regions spermatogenesis was seen to be in prog- 

 ress as far as the formation of spermatids. None of the latter, 

 however, was ever found in process of transformation into the 

 spermatozoon. 



Upon examining sections of the testis the first thing to strike 

 the attention was the great scarcity of seminiferous tubules. 

 While a few of these were visible in sections from nearly all regions, 

 they existed for the most part as narrow scattered tubules (fig. 1) 

 surrounded by vast areas of intervening tissue, or more frequently 

 as small island-like groups of a few larger tubules in a more or less 

 homogeneous field of connective tissue and stroma cells (fig. 2). 

 At times, however, limited areas (fig. 3) would be encountered 

 in which the seminiferous tubules were almost as plentiful as in 

 normal non-hybrid individuals. One hybrid in particular differed 

 markedly from the others in having a plentiful supply of tubules 

 throughout the most of the testis. In certain of these tubules divi- 

 sion stages of spermatogonia and first spermatocytes were plentiful. 

 Less frequently dividing spermatocytes of the second order were 

 found. Side by side with such tubules, and often in greater 

 numbers, would be found other tubules in process of degeneration. 



The seminiferous tubules of the guinea have a thicker investing 

 rind or wall than do those of the ordinary domestic cock, and while 

 there is considerable fluctuation in the diameter of different 

 tubules in both species, on the whole, the former has a noticeably 

 broader, coarser looking type of tubule. There is also shghtly 

 more interstitial tissue in the testis of the guinea. In all of these 

 respects, as well as in the general appearance of the various mitoses 

 the hybrids approximate more nearly the condition found in the 

 guinea. 



In the hybrids, as already stated, the seminiferous tubules 

 were usually few in number and widely separated by intervening 

 tissue. Under the low power of the microscope this inter-tubular 

 field ordinarily had a homogeneous cellular appearance, but 

 under a moderate or high power the cells were seen to be arranged 

 in irregular cords or strands, although this corded appearance 

 often graduated indistinguishably into a homogeneous field. The 

 stroma or interstitial cells occupying most of the inter-tubular 



