BIGELOW: NUCLEAR CYCLE OF GOXIOXEMUS MURBACHII. 343 



chance of error. A typical specimen, and one which shows the relations 

 of the nuclear structures perhaps as clearly as any, is represented in 

 Figure 127. There are in this case twelve or thirteen beaded segments 

 very loosely connected with one another and with the nucleolus by 

 exceedingly delicate linin threads. The number of " beads " in each 

 segment varies from four or live to eight or nine, and similar variation 

 was seen in all the cells examined. The segments themselves, which 

 are very stout and sharply outlined, vary both in length and form, being 

 either nearly straight, or U-shaped, or variously bent and twisted. 

 Their number seems also to be variable, there being as a rule from 

 twelve to fifteen ; in many cases, however, several may be so intimately 

 connected as to make their resolution impossible. I believe, that owing 

 to this variability, they cannot be homologized with chromosomes, though 

 unfortunately on this point, which is one of great theoretic importance, 

 their later history throws no light. Their frequent exhibition of U-, V-, 

 and Y-shaped forms (Figs. 126, 127) at first suggests the possibility that 

 this may be a stage of synapsis ; but the internal evidence on this point 

 is too scanty to be convincing, and the later stages of the oocyte are 

 such as probably to forbid our accepting this view. I, therefore, believe 

 that, if we are to homologize this stage with any part of the usual pro- 

 phase of mitosis, it must be with the spireme. 



The central part of the nucleolus (Figs. 125-127) is, in addition 

 to the chromatic structures, a constant feature of the nucleus. This 

 body, which is spherical, frequentlj' vacuolated, and very much smaller 

 than the compound nucleolus present at the commencement of this 

 apparent prophase, appears to persist from the telophase of the last 

 oogonial division till the time when the ripe oocytes are released. 

 Finally, at no time, at least up to this point, can any trace of centro- 

 some, sphere, or other archoplasmic structure be detected. 



The steps in the process from the resting stage to the formation of 

 the "segment" or "modified spireme" stage just described are traced 

 very easily, but the later changes are much more difficult to follow, and 

 still remain somewhat obscure. "We should naturally expect the chro- 

 matin-segment stage to be followed by division ; but, although I have 

 searched several hundred sections, I have found no evidence whatever 

 that this is the case. It seems, on the contrary, almost certain that this 

 stage is the culmination, so to speak, of this phase of nuclear activity, 

 and that it is followed by regressive changes resulting eventually in the 

 assumption once more by the nucleus of the so-called resting condition. 

 Since this conclusion — that this apparent prophase is not followed by 



