SPERMATOGENESIS OF THE RABBIT. 303 



division the nucleus is somewhat crescent shaped, but soon 

 assumes a spherical form. This stage develops no spireme or 

 leptotene threads. The chromosomes, eleven in number, imme- 

 diately migrate into the equatorial plate to form a very dense 

 mass which at times appears almost homogeneous, so closely 

 are the chromosomes drawn together (Fig. 34). In this division 

 the chromosomes, in migrating toward the poles, often appear 

 as solid black ring-like masses with apparently no segments 

 representing the individual elements. Dense fibers seem to be 

 interwoven in the mass of chromosomes (Figs. 35, 36). It is 

 seldom that the chromosomes can be distinguished in these 

 stages. The X and the Y elements also as a rule lose their 

 identity, but occasionally they can be identified by their presence 

 in the center of the ring, connected by chromatin strands to the 

 ordinary chromosomes (Figs. 37, 38). 



The chromatoid body appears to undergo no division in these 

 stages, following either one or the other of the chromatin masses. 

 We thus find that approximately one-fourth of the total sperma- 

 tids contain the chromatoid body. 



6. TRANSFORMATION OF THE SPERMATIDS. 



As soon as the division is complete, a new nuclear wall is 

 immediately formed. The chromosomes as such disintegrate 

 but the chromatic material soon condenses at the periphery of 

 the nucleus (Figs. 39, 40). In this manner nearly all of the 

 chromatic material is condensed, leaving one part which in 

 every case is found somewhere near the center of the cell (Figs. 

 41, 43) and which may represent the accessory element. Some- 

 times there are one or more smaller bodies which may be remnants 

 of the disintegrating ordinary chromosomes because they do not 

 persist for any length of time. The large central body can be 

 traced through the stages of further condensation and almost 

 to the completely developed sperm. 



After all of the chromatic material has condensed, the centro- 

 some makes its appearance and moves close to the nucleus (Fig. 

 41). It here gradually becomes immeshed in strands of chro- 

 matic material within a slight infolding of the periphery of the 

 nucleus. By a continuation of this process it soon becomes 



