BIGELOW: NUCLEAR CYCLE OF GONIONEMUS MURBACHII. 341 



the chromosomes do not persist as such; they do not retain their indi- 

 viduality during the later growth period of the oocyte. Xor is there 

 during the telophase any evidence of the occurrence of synapsis, so that 

 we must, no doubt, look for the occurrence of this process at a much 

 later stage. 



2. TJie Oocytes. 



At the close of the last oogonial division the daughter cells, now 

 oocytes, enter upon a typical " resting" stage, during which they undergo 

 very considerable growth. This, however, is not the commencement of 

 their final growth period, for very significant nuclear changes take 

 place prior to that period. An oocyte in this stage is represented in 

 Plate 5, Figure 120. The nucleus exhibits the usual reticulate condi- 

 tion already described in corresponding phases both of somatic and of 

 male germ cells (pages 296, 302), there being, as a rule, a single very large 

 nucleolus, from which delicate linin strands radiate outward through the 

 rather dense karyoplasm. The nucleolus itself shows a deeply staining 

 external shell enclosing a more transparent central mass. The cytoplasm 

 is finely reticulate and occasionally encloses metaplasmic masses, but 

 no trace whatever of any archoplasmic structures, such as Nebenkern, 

 sphere, or centrosome, can be detected. When treated with the Auer- 

 bach mixture, nuclear membrane, karyoplasm, reticulum, and karyosomes 

 select the acid, while the entire nucleolus selects the basic dves. The 

 cell grows until the nucleus attains a diameter of about 8.5 p, when 

 there occur nuclear changes which suggest the prophase of an ordinary 

 mitosis. The occurrence of such appearances is remarkable, for, as we 

 shall see (page 345), it is almost certain that they do not lead to any 

 cell division whatever; therefore they must be considered in detail. 



PseudqpropJiase. — The first change in the nucleus is, as in ordinary 

 mitosis, a thickening of the reticulum (Fig. 121), which now, more con- 

 spicuously than before, radiates from the nucleolus, while the karyosomes 

 increase in both size and staining capacity. At the same time the karyo- 

 plasm becomes gradually less and less dense until at last it disappears 

 altogether, leaving the nucleus in the typical " empty " condition. 

 Many karyosomes now come to lie along the course of the threads of the 

 net, instead of only at its nodes, as was previously the case ; and at the 

 same time the nucleolus suffers a decrease in bulk (compare Fig. 120 

 with Fig. 122). As the karyosomes, lying along the strands, increase in 

 number, they become more or less crowded together, thus forming 

 rather definite chromatin segments having a " beaded " appearance. Fig- 



