418 



ELMER L. SHAFFER. 



which are similar to those found in the protobroque and deuto- 

 broque (preleptotene) nuclei. In the later stages these bodies 

 become closely associated (Text-fig. 3, Figs. 81, 84) and persist 

 as definite chromatin nucleoli. A true plasmosome is also present 

 in these stages which becomes vacuolated and grows in size with 

 the age of the oocyte (pi., Figs. 44, 46). In the older germinal 



$, r n 



TEXT-FIG. 3. Oocyte of post-synaptic period, showing mitochondria arranged 

 in perinuclear zone, and two chromatin nucleoli (cr.n.) and a plasmosome (pi.). 



vesicles, the two chromatin nucleoli may persist (Fig. 87), but 

 more commonly a single large chromatin nucleolus is found 

 together with six to eight smaller nucleoli (Fig. 46). 



It is difficult to say whether the two chromatin nucleoli really 

 represent persisting sex-chromosomes and are therefore homol- 

 ogous to the chromosome nucleoli of the spermatocytes. There 

 is some evidence that this is the case. The disappearance of the 

 definite nucleoli during the synaptic stages (leptotene and pachy- 

 tene) leads me to believe that they are resolved into chromatic 

 threads which go through a synaptic process similar to the 

 autosome threads. The fact that there are ten pachytene threads 

 in the bouquet stage indicates that all the chromosomes are in 

 synapsis. The reappearance of the two chromatin nucleoli in 

 the strepsistene stages are perhaps brought about by a re-con- 

 densation of the synaptic threads representing the sex pair 

 resulting in the formation of the two compact chromatin nucleoli. 



