LIFE-CYCLE OP " CYSTOBIA " IRREGULAETS (mINCH.). 41 



spheres or nuclear spindle^ and tlie former are equally absent 

 from the resting nuclei in other parts of the jDreparation. 

 Neither is there any indication of karyokinetic apparatus 

 in the eight-nuclear stage, and as division-centres are very 

 easy to see later on, it is not likely that I have overlooked 

 them here. Hence, I maintain there is a very great 

 probability that the preceding divisions are amitotic also. 

 Another strong point in favour of this view is the fact that, 

 when asters and nuclear spindle appear at first, and the 

 division of the " segmentation "-nucleus ^ is mitotic, that of 

 the resulting daughter-nuclei is so too, and the division- 

 centres in connection with them are very apparent (Mono- 

 cjstis, Diplocystis, Lankesteria, see Cuenot, Siedlecki, 

 Prowazek [loc. cit.]). I think this fact and the obviously 

 direct division of a daughter-nucleus of the third generation 

 (fig. 47 c.) are snflScient to warrant my saying that the first 

 nuclear divisions in C. irregularis are completely ami- 

 totic." 



We may now take a bird's-eye view of one or two sporu- 

 lating Gregarines at about this period, in order not to forget 

 the whole in considering a part. Figs. 39 and 40 show two 

 such couples, both from the blood-vessel, and neither in the 

 least indicating, by cyst-like shape or the possession of cyst- 

 membranes, any appearance of encystment. In both Gre- 

 garines the persistent septum entirely separates the nuclei 

 derived from the parent-nucleus of each associate. Fig. 39 

 is a section and so only few nuclei are seen ; altogether there 

 are about thirty. Fig. 40 is drawn whole from a stained 

 preparation, and in this the multinuclear condition is well 



' That is, the functional poition of tlie original sporont-nucleus remaining 

 after the unnecessary constituents have been expelled. 



2 It would seem, moreover, as if this fact stood in some relation with the re- 

 tention of the karyosomes in tiie nucleus. For, in G. cuneata and in Seleni- 

 dium, the two instances above referred to as resembling Cystobia in the 

 latter respect, the first nuclear divisions are equally amiLotic, although differing 

 somewhat from those in C. irregularis in being of the " multiple " type 

 instead of by simple binary fission. 



