NUCLEOLI IN EUSCHISTUS VARIOLARIUS. 225 



chromatin of the young oocytes is as homogeneous as that of 

 the spermatocytes of Photos I, 4 and 5. 



We find nothing in these germinal vesicles answering to Telly- 

 esniczky's karysomes, unless he would homologize the aggre- 

 gations of chromatin shown in Photos 12, 15 and 16 with these 

 structures. These aggregations of chromatin are too numerous 

 to be interpreted as the seven bivalent chromosomes of the later 

 stages, or as their fourteen component univalents. In the germi- 

 nal vesicle of Photo 15, for example, there are about fifty clumps 

 of chromatic substance. Perhaps these clumps of chromatin cor- 

 respond more closely to the segregated granules Wassilieff ('07) 

 describes in the nucleus of Blatta. These clumps, he says, are 

 too numerous to be interpreted as representing individual chro- 

 mosomes. Later he finds that they disintegrate and are scattered 

 throughout the nucleus like a fine dust ; the delicate threads of 



o 



the later stages being formed at the expense of this dust-like 

 substance. 



In the germinal vesicles of Euschistns variolarius the chromo- 

 somes first appear as extremely fine threads, which seem to arise 

 as a concentration of the distributed granular mass, these granules 

 gradually disappearing as the threads become more defined. 

 Photo 17 shows a germinal vesicle at the stage just before the 

 chromosomes appear the chromatin is still distributed as gran- 

 ules throughout the nucleus, although the size of this nucleus is 

 nearly equal to many of the germinal vesicles in which the chro- 

 matic threads are fully developed. In Photos 18 and 20 we see 

 the delicate chromatic threads just appearing, as yet very indis- 

 tinct, and in the later stage shown in Photo 21 the threads are 

 more distinct but too much tangled to warrant any precise in- 

 terpretation. In later stages, however, we can often trace among 

 the filaments, an unbroken thread, so long that it cannot possibly 

 be interpreted as one of the fourteen univalents, it must represent 

 at least two univalents attached end to end. Again some of 

 these threads are long enough to justify the inference that they 

 represent even more than a bivalent, indicating that in Euschistus 

 the chromosomes emerge from the rest stage not as univalents, 

 but as long threads representing at least one or more bivalents, 

 thus supporting the observations of those who believe that bival- 



