2Q6 L. J. BACHHUBER. 



writer has found the same condition, although to a lesser degree 

 than in the rabbit, namely, the strong tendency of the parts 

 within the nucleus to mass, hiding many of the individual 

 structures, and leaving much to be desired in the form of im- 

 proved methods. In the rabbit, the chromosomes always 

 agglutinated, permitting but few chromosomal counts. Because 

 of this, the only stages in which chromosomal counts were 

 possible with any degree of accuracy were the primary spermato- 

 cytes. In later stages it was decidedly more difficult to find 

 stages in which counts were possible. 



In the rabbit, the structures to be followed more readily are, 

 first, the two accesory chromosomes and second, the chromatoid 

 body. After the spermatogonial stages, the accessory chromo- 

 somes could nearly always be identified and rather easily traced. 

 The chromatoid body, similar to that described by Wilson (1913), 

 whose origin could not be determined, can be easily followed, 

 beginning with the primary spermatocytes, and can even be 

 identified when it is cast off from the transforming spermato- 

 somes. 



The other structures displayed in the spermatogenesis of the 

 rabbit, and the various processes connected with them, do not 

 differ materially from the corresponding stages described for 

 other forms. In the following pages, the process of spermato- 

 genesis, in so far as it could be determined, will be taken up in the 

 order of the successive stages of spermatogonia, primary and 

 secondary spermatocytes, spermatosomes, and the fully de- 

 veloped spermatozoa. 



i. ZONES OF PROLIFERATION. 



Throughout all the tubules of the testes, there appear small 

 areas in which active proliferation reveals almost every stage 

 of spermatogenesis. These areas are not, how r ever, confined 

 to any particular section or part of the tubule. All indica- 

 tions of the active zones go to show that a certain area may be 

 active for a period, then halt in its activity while a nearby area 

 becomes active in spermatogenesis. There are thus, scattered 

 throughout each of the tubules, areas of active proliferation and 

 areas of rest. In each of these areas of activity usually there 



