Mr. J. E. S. Moore — Observations upon Amoeba. 151 



these problems, it would be interesting to find anything com- 

 parable to such nuclear differentiation in the other Protozoa. 



Turning to the Rhizopods, we find a great variety of 

 nuclear conditions ; for example, those described by Gruber 

 in a compendious summary published in the ' Zeitschrift 

 fiir wissenschaftliche Zoologie^ *, and, again, in his ' Studien 

 iiber Amoben ' f, where there is an admirable description of 

 the mono- and multinucleate forms of Amoebge, of the great 

 diffused nucleus of A, proteus^ and of the numerous vesiculate 

 nuclei of Pelomyxa. 



The most interesting thing, however, about these nuclei 

 seems to be the fact that whereas the multinuclei of Pelomyxa 

 divide by a process equivalent to karyokinesis, the great 

 diffused nucleus of A. proteus^ according to the beautiful 

 figures of Schulze and others, divides akinetically in the 

 strictest sense of the term. So also the primary division of 

 the nuclear element in Arcella, when nearing the spore- 

 forming stage, is typically karyokinetic ; but whether this 

 process of multiplication is maintained is not apparent. 



The numerous nuclear elements in the Heliozoa appear, 

 according to Gruber, to increase in a mitotic fashion, while 

 the duplication of the nuclei in Euglypha alveolata is repre- 

 sented as proceeding by more than one method. 



In an interesting paper in the * Zeitschrift fiir wissenschaft- 

 liche Zoologie ' X Verworn describes m Diffiugia lohostoma tlie 

 conjugation process and the existence of corpuscles answer- 

 ing to the micro-nuclei of the Ciliata. Of these structures he 

 says : — " Neben den Individuen, welche die obenbeschrie- 

 benen normalen Kernverhaltnisse zeigten, fanden sich sehr 

 haufig audi einzelne lebende Exeraplare mit ganz abweich- 

 endem Verhalten. Diese Individuen besassen zwar auch den 

 grossen runden, blassen Kern, mit ganz normalem Aussehen 

 . . . ausser ihm noch einen zweiten, der eine vollig verschie- 

 dene Beschaffenheit aufwies ; " and further, " Offer fand ich 

 Konjugationen, in denen, ausser dem normalen grossen Kern, 

 keine kleine Kerne vorhanden waren." He sums up thus : 

 " Dass der Kern eine bedeutsame RoUe bei der Konjugation 

 spielf, indem die Konjugation charakterisirt ist durch das Auf- 

 treten je eines kleinen eigenthiimlich gestalteten Kerns neben 

 dem gewohnlichen, der moglicherweise dem Nebenkern der 

 Ciliata Infusorien entspricht, und ferner dadurch, dass diese 

 kleine Kerne der beiden Individuen wahrend der Konju- 

 gation in nahe Beziehung zu einander treten." 



* Bd. xl. 1884, pp. 121-152. 



t " Eine Mittheilung iiber Kernvermehrung imd Scliwaraierbildnng 

 bei Siisswasser-Rhizopoden," iliid. Bd. liii. 1892, pp. 114-118. 



I Bd. 1. 1891, p. 443, Taf. IS. 



