SPERMATOGENESIS OF THE HORSE. 3! I 



body does not contribute in any visible way to the formation of 

 the spermatozoon. The foregoing facts also indicate that great 

 care must be exercised in interpreting the significance of bodies 

 which appear like chromosomes, but really are something entirely 

 different and no positive statements can be made regarding their 

 meaning unless their entire history can be definitely traced. 



It is very probable that a body similar to the chromatoid body 

 in the horse also exists in the pig. In speaking of a small chro- 

 matin body which frequently occurs in the first spermatocyte 

 division of the pig (Wodsedalek, '13), I make the following 

 statement: "Occasionally a small chromatin body is present in 

 this first spermatocyte division (Figs. 28, 31, 32, 35 and 37). 

 Fig. 31 shows such a body passing to the same pole with the 

 accessories, in advance of the other chromosomes. Fig. 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. While the small body can be 

 seen frequently, as a rule no such element can be detected, and 

 while it may possibly be comparable to the small pair of chromo- 

 somes 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." 



Further investigation regarding the body in question in the 

 pig will be taken up presently. It might also be mentioned here 

 that the chromatoid body is present in the germ-cell of the bull. 

 A complete account of its behavior in that animal will be pub- 

 lished later. 



XII. SUMMARY. 



1 . Thirty-seven chromosomes differing somewhat in size occur 

 in the spermatogonia. One, the accessory, is distinctly larger 

 than the others. 



2. In the spermatogonial division the accessory divides a 

 little in advance of the other chromosomes. 



3. Nineteen chromosomes appear in the primary spermatocyte 

 division, of which eighteen are evidently bivalent and the other 

 is the accessory. 



