398 EDMUND B. WILSON. 



vacuole-like space (Fig. 26). In slightly later stages one of 

 these granules rapidly enlarges and may soon be distinguished 

 as the chromatoid body (Fig. 27). The other granules seem in 

 many cases to disappear, though they may often be distinguished 

 in addition to the large chromatoid body up to a late stage and 

 even during the divisions (Figs. 29, 30, 10). No evidence can be 

 found that any of these granules are extruded from the nucleus 

 (as has been suggested for the "chromatoid Nebenkorper" by 

 several earlier observers) ; and it may be pointed out that 

 throughout all these stages both kinds of nucleoli are always 

 clearly visible within the nucleus. Neither can I find evidence 

 of any connection between them and the centrioles, which are 

 first seen in much later stages, lying close against the nuclear 

 membrane. 



The chromatoid body reaches its maximum size in Stage / or 

 the "confused period" (Fig. 30) when it becomes a most con- 

 spicuous element which from this time forward undergoes little 

 or no change until long after its delivery to the spermatids. 

 During this whole period it is always surrounded by a clear, 

 vacuole-like space, and may thus be identified at every stage, 

 even during the divisions. The examination of hundreds of 

 cells during this whole period in P. senilis has shown only two or 

 three cases in which more than one such large chromatoid body 

 is present. Its single character seems therefore to be typical 

 of this species. In P. juniperina, on the other hand, two such 

 bodies, equal or unequal in size, are more often seen. 



From the early post-synaptic stage forwards the nuclei always 

 contain a well defined, conspicuous plasmasome, and one or two 

 intensely stained chromosome-nucleoli. When single, the chro- 

 mosome-nucleolus is about twice the size shown when two are 

 present (Figs. 26-30). In the earlier stages these bodies are 

 often more or less irregular in form, or elongated. In later stages 

 they are nearly spheroidal, and appear exactly similar, but for 

 their position, to the extra-nuclear chromatoid body. During 

 the prophases [the plasmasome disappears, while, as already 

 stated, the chromosome-nucleoli are converted into chromosomes 

 of looser texture, somewhat elongated, and like the bivalents 

 conspicuously split lengthwise. In the final prophases all the 



