52Ô Theophilus s. Painter, 



that the nucleus itself is increasing in size, is „swelling- with the 

 accumulation of nuclear sap", as it is often expressed. This increase 

 in size may be clearly seen by comparing Figs. 12, 13, 14 or 15 

 with 19, 20 or 23. 



The variation in the number of hétérochromosome elements in 

 these cells of the rest period presents one point of extreme interest. 

 It is immediately after the autosomes have become resolved into a 

 reticulum that the nucleoli show the greatest variation in the number 

 present in the cells. In Figs. 12 and 13, we have two cells of 

 the rest period which lie side by side and which represent, I believe, 

 the two daughter cells from a spermatogonial division. The cell 

 shown in Fig. 12, have a very small size; but the nucleoli have 

 already fused, while, in the cells shown in Fig, 13, there are still 

 four nucleoli to be seen. In the latter case, it should be noted 

 that two of the nucleoli are larger than the other two. In the cell 

 shown in Fig. 15, we find four nucleoli also two of which are larger 

 than the others although the size differences in this case are not 

 so striking. In Fig. 16, we find only three nucleoli present. In 

 Figs. 17 or 18, there are two nucleoli but in both of these cases the 

 shape of the nucleoli would indicate that they are fusing with some 

 object. Such cells contain without doubt the accessory elements 

 together with the ctetosomes. 



It is very difficult to say, judging from the rest period, just 

 what percent of the cells carry the small nucleoli, which we believe 

 represent the ctetosomes, and what percent lack these bodies. As 

 we look at any one cell we must keep in mind the possibility that 

 fusion may have taken place between the nucleoli. There is one 

 point which will materially assist us here, and that is, when the 

 smaller nucleoli fuse with the accessory cliromosome elements the 

 resulting mass always appears somewhat irregular in outline, as is 

 shown in Figs, 22 and 23 ; and when these bodies are not present 

 the two larger nucleoli form a rounded mass with regular outline 

 (Figs. 20 or 21). 



Wilson has noted the same behavior in the supernumeraries of 

 Metapodius (Study VI). Tlie iri-egular mass formed in Maevia vittata 

 probably is an indication that these small nucleoli are simply drawn 

 to the larger as perhaps being of the same general chemical nature, 

 without losing their identity, while the two accessory chromosome 

 nucleoli undergo a moie complete fusion when they are alone. The 

 fusion of the smaller nucleoli would be, then, only apparent and not 



