66 ROBERT H. BOWEN. 



pears to break up partially." In this unsatisfactory manner the 

 account closes. The probable fate of the spireme will be touched 

 on in a later paragraph. 



To return now to the plate-work in the nebenkern of Heinip- 

 tera. The process of condensation having reached the stage of 

 Figs. 5 a'nd 6, the plate-work begins now to become much more 

 open and irregular ; and in the immediately succeeding stage the 

 resemblance to an onion has been largely lost (Figs. 7 and 8). 

 The running together of the chromophilic material has resulted in 

 the disappearance of a part of the plate-work, which now consists 

 of a few much-folded plates whose optical cross-sections are 

 usually rather simple. Fig. 7 is an especially striking one, since 

 in this case the outline forms a perfect spireme reminding one of 

 Gatenby's account. Fig. 8 is another example of the same stage, 

 and by changing the fine adjustment slightly, the optical section 

 can be converted into a perfect spireme. By a similar change of 

 focus, the spireme of Fig. 7 can be transformed into an appear- 

 ance similar to that of Fig. 8. If further proof of the plate-like 

 rather than thread-like structure is necessary, it can be provided 

 by a cross-section of the nebenkern (Fig. 9). (Figs. 8 and 9 are 

 from the same cyst of spermatids.) Comparing this cross-sec- 

 tion with Fig. 6, it is clear that the chromophilic substance is still 

 arranged in a plate-work form, but now a very irregular one. 

 It is also of interest to note that the plate-w r ork seems to end at 

 opposite points on the surface of the nebenkern, thus marking 

 the future division plane of the mass as a whole. 



At a slightly later stage (Fig. n) the plate-work has become 

 still more condensed and simplified, while the chromophilic sub- 

 stance of which it is composed seems to< be decreasing in actual 

 quantity. At this time, as is shown also by cross-sections (Fig. 

 12), the plate-work forms a flattened, ovoidal core, the exterior of 

 which is now delimited by a smooth, regular layer. Internally a 

 single, much-folded septum is inserted in this outer layer along 

 the future division plane of the nebenkern. The further conden- 

 sation of the plate-work now progresses rapidly, the ovoidal core 

 of chromophilic substance shrinking considerably in. size, while 

 the folded, internal septum smoothes out to form a flat, regular 



