THE RELATION BETWEEN AMITOSIS AND MITOSIS. 195 



group of the nuclei in most of which the spireme is apparently 

 breaking up and disappearing. It stains less deeply than in earlier 

 stages and appears to be separating into irregular masses. Fig. 

 27, j5(Pl. XII.), shows an exceptionally clear case, in which some 

 portions of the spireme are apparently breaking up into granules. 

 Figs. 27, C, and 27, D (PI. XII.), show still other cases. It will 

 be observed that the nucleolus retains its staining power : as a 

 matter of fact it undergoes no visible change. 



Except for the spireme or its remnants the nucleus shows with 

 the usual degree of extraction no visible structural features. As 

 it increases in size the nuclear membrane becomes increasingly 

 difficult to distinguish and finally disappears, so that what was 

 formerly the nucleus appears merely as a cavity in the cytoplasm 

 containing the nucleolus and irregular shreds and granules of 

 chromatic substance usually situated at one side (Figs. 27, B, 27, 

 C, 27, D, 28, PI. XII.). The whole appears as if degenerating. 

 In these and the following figures the boundaries of the nuclear 

 cavities and the spaces in the cytoplasm which remain in the 

 later stages are indicated by broken lines. 



But the observations now to be described afford very strong 

 evidence in favor of the view that these nuclei do not undergo 

 complete degeneration. In and about these cavities containing 

 the remains of the spireme and the nucleolus very small new 

 nuclei with one or a few small granules of chromatin appear to 

 be formed. In Fig. 28 (PI. XII.), one such nucleus is shown 

 in one of the cells : in Figs. 29, A, and 29, B (PI. XII.), two appear 

 in each cell : in Fig. 29, C (PI. XII.), is one a little larger than 

 the preceding ; in this case the fragmenting nucleus lies in a 

 cytophore with spermatids already formed and from one of which 

 a spermatozoon is developing : in Fig. 29, D (PI. XII.), are again 

 two of the small nuclei. The nature of the process appears to 

 be somewhat as follows : as the old nuclear membrane breaks 

 down the cytoplasm encroaches more or less upon the nuclear 

 cavity and a new membrane forms about some of the particles or 

 masses of chromatin. This is not very different from what occurs 

 in various forms when a single chromosome or a few chromo- 

 somes are separated from the rest during division. 



But the new nuclei are not always so small as these shown in 



