ON THE PROTOPLASTID BODY, ETC. 325 



a great number of daughter nuclei, the exact fate of which 

 has not been ascertained ; but the process of the successive 

 multiplication of these nuclei appears to be carried on in a 

 similar manner to the normal karyokinetic division of the 

 nuclei in metaplastid cells (fig. 31). In Actinospherium 

 Eichhornii the vesiculate resting nuclei (fig. 1) develop 

 chromosomes or separate chromatic elements, and then go 

 through the regular course of karyokinesis represented in 

 figs. 2-6. 



In the Rhizopod Arcella Gruber (2) represents the great 

 nucleus dividing up in a typically mitotic fashion (figs. 29, 

 30), and during the fissiparous bipartition of Ettglypha alveo- 

 lata, Schewiakoff (3) has shown that karyokinesis, with its 

 complement of chromosomes, spindle, and even centrosomes, 

 is carried out in full (figs. 27-28). 



Last, but not least, it is known that the great nucleus 

 of many Rhizopods may increase by akinesis in the strictest 

 sense of the term ; and the nucleus of the Rhizopods (fig. 

 32) appears thus, even in the metamorphoses which it may 

 undergo, to be strictly comparable to that of the metaplastid 

 cells. 



In the great majority of Infusoria, both ciliate and flagel- 

 late, the nuclear structures appear at first sight to be radi- 

 cally unlike those obtaining among metaplastid cells, because 

 in these forms of protoplastids there, are two kinds of nuclei, 

 which, when they are fully formed, differ entirely from each 

 other. The Macro — or larger of these two kinds of nuclei, 

 multiply by a process practically equivalent to akinesis ; 

 while the Micro— Micro-nuclei pass through all the normal 

 karyokinetic phases. It has been shown, however, by 

 Maupas (4), R. Hertwig (5) and others, that the macro- 

 nuclei of the Ciliate Infusoria arise periodically from 

 more or fewer of the nuclei produced by karyokinetic 

 division from the micro-nucleus ; the elements which 

 form the macro-nuclei being indistinguishable from those 

 which persist as micro-nuclei when they are freshly formed. 

 It consequently follows that the Ciliated Infusoria are to 

 be regarded as multi-nucleate protoplastids, in which 

 some of the nuclear elements have become structurally 



