MT.KMATOGENES1S OF THE CADDIS-FLV. 65 



as a rule re-ts outside the chromatin mass which at this time 

 in i upics about half the nucleus. At this time the body seems 

 to IH- a part of the spireme. In the next stage when the chroma- 

 tin conic- out <f -> napsis this body appears as a pan of the much 

 thickened -pin-me thread (Figs. 17-21). It is quite large at this 

 time and much resembles a nucleolus in its intense -taining 

 n MI i ion- lull it i- -pindle shaped and from each end run- out the 

 continuation ot tlie -piremc thread. In the triple stain at thi- 

 time it -till take- thesafranin color. A still closer examination 

 -how- that the threads leading up to this body are double and 

 the body itself is divided into two halves by a longitudinal furrow. 

 It lie- .n thi- time, when seen in side view, as a flat spindle- 

 -haped figure immediately pressed against the nuclear wall. It 

 now tv-embie- \t-ry much the accessory chromosome as drawn 

 l>> M<< li, in hi- Fig. 2, except that he at this period dis- 



co\rrcd no l.n-.ik and the body that he drew was proportionally 

 coii-ider.ibly l.uxi r. He describes and figures a stage (Fig. 5) 

 \\here thi- liod\ goes into a spireme of its own but no split \\a- 

 ob-cr\ed in ihi- -eparati- thread. Considering the subse< jucnt 

 behavior of thi- body the formation of a tetrad and of chronio- 

 somes, -mli .1 -plit i- to be expected. A split was to be observed 

 in thi- chromatin nm leolus of Platyph v/a.v; its spireme is a part 

 ot tin -pin me formed from the remainder of the chromatin. 

 The -plit in it becomes more marked (Fig. 19) and the body 

 finally open- out a- a lo/enge-shaped tetrad (Fig. 21). At thi- 

 time the other ihiomosomes have not yet formed, although the 

 lon-iiMilinal -plit has taken place. In some cases it look- as 

 though the tran-\er-e splits have already occurred, but the thread 

 -till remain- int.n i with this body as a part of it. This black 

 -taming tetrad is one of the most conspicuous parts of the nucleu- 

 at thi- time i Fig. 2l). 



The other chromosomes are now formed and assume the pe- 

 culiar -h.ipe- characteristic of them at the time before they form 

 the tetrads. Thi- body is still recognizable at thi- time on 

 account ot it- regular lozenge shape while the other- are in the 

 form ot K's, Y's and various other twisted shapes (Fig. 23). At 

 the next -tage. however, when all the chromosomes have become 

 tetrad- thi- body is indistinguishable from them (Fig. 24). 



