SPERMATOGENESIS OF THE PIG. 15 



It is obvious that as far as chromatin content is concerned the 

 division of the primary spermatocyte gives rise to two dissimilar 

 cells, one of which receives eight chromosomes, and the other 

 eight plus the two accessories or ten chromosomes (Fig. 38). 

 Figure 39 is a drawing of one end of a late anaphase of such a 

 division showing eight chromosomes, and Fig. 40 shows the 

 other end which received eight of the ordinary chromosomes and 

 the double accessory. 



Occasionally a small chromatin body is present in this first 

 spermatocytic division (Figs. 28, 31, 32, 35 and 37). Figure 31 

 shows such a body passing to the same pole with the accessories, 

 in advance of the other chromosomes. Figure 32 represents an 

 earlier stage of much the same thing. In Fig. 35 it can be seen 

 passing to the opposite pole, and Fig. 37 represents an extremely 

 rare case where two such bodies are present, one somewhat larger, 

 passing to either pole, even in advance of the two accessory 

 chromosomes. Figure 28 shows the body outside of the main 

 ring of chromosomes. While the small body can be seen fre- 

 quently, as a rule no such an element can be detected, and while 

 it may possibly be comparable to the small pair of chromosomes 

 found so constantly in some of the Tracheata, my present data on 

 its irregular occurrence and behavior do not permit a conclusion 

 regarding its significance. 



SECONDARY SPERMATOCYTE. 

 i. Dimorphism. 



The dimorphism of the secondary spermatocytes, which re- 

 sulted from the last division, is again expressed in the resting 

 stage that sometimes follows. Approximately half of them 

 showed, under proper decolorization, two large chromatin nucleoli 

 (Fig. 41) while in the others only the small nucleoli appeared 

 (Fig. 42). The nucleoli retain the usual deep staining capacity, 

 and as was true in the previous stages, even when all the other 

 material is almost totally decolorized, the nucleoli remain very 

 conspicuous. Frequently, both primary and secondary sperma- 

 tocytes were found dividing in the same field, which fact seems to 

 suggest that at times there is no intervening period of rest be- 

 tween the two divisions, or that it is very brief. Figure 43 



