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



nucleus and attraction sphere, which may well retain the 

 name of " Nebenkern "*. 



In May last I succeeded in adducing evidence in support of 

 the view, first initiated by Flemming I believe, that the 

 karyokinetic division of a cell is in reality an expression of 

 two metamorphoses, each to a certain extent independent of 

 the other f : one affects the attraction-sphere and the dividing 

 central bodies, the other the nucleus and the dividing chromo- 

 somes. And it is probable tiiat this apparent duality in the 

 metamorphosis may have had much to do with the modern 

 conception that the protozoan micro-nucleus is more or less 

 equivalent to the metazoan central body, and the metazoan 

 chromatic element to the protozoan macro-nucleus |. 



1 am not of this opinion, for I fail to see how a structure 

 jiresenting all the features of a karyokinetic division, such as 

 is seen in the micro-nucleus of a Paramcecium or a Colpidium, 

 can be compared with the central body of a cell, metazoan or 

 other. 



That the great macro-nucleus, where it exists in the Infu- 

 soria, is intimately related in some way or other to the 

 digestive activity of the animal seems highly probable. 

 Indeed it is difficult to see what other functions could be 

 assigned to it ; and the Ciliate as a single cell will have to 

 perform all those secretive operations which in more highly 

 specialized organisms would be told off to particular glandular 

 organs §. 



Thus it becomes possible that the existence of the " Neben- 

 kern " in many gland-cells of the Metazoa (if that structure 

 can be shown to be there normal) may offer an analogy to 

 that differentiation of the nuclear elements apparent in the 

 ciliate Infusoria. Whatever be the ultimate solution of 



* See " Contributions to Morpbol. and Physiol, of the Cell," Macallum, 

 Trans. Canadian Institute, vol. i. pt. 2 ; Steiuhaus, " Ueber parasitare 

 Einschliisse in den Pancieaszellen der Amphibien," Ziegler's Beitrage 

 zur Path. Anat. und zur Allgem. Path. Bd. vii. p. 367 ; Nussbauni, 

 " Ueber den Bau uiid die Thiitigkeit der Driisen," Arch, fiir mikr. Anat. 

 Bd. xxi. p. 296. 



t Unpublished paper in the hands of the editor Quart. Journ. Micr. 

 Sci. 



X Cf. II. E. Ziegler, ' Biologisches Centralblatt,' Bd. xi. uos. 12 and 13, 

 pp. .372-389 ; and Biitschli, " Ueber die sog. Centralkorper der Zelle und 

 ihre Bedeutung," Verhandl. d. Naturhist.-med. Vereins zu Heidelberg, 

 Bd. iv. 



§ This view receives some support from a consideration of the multi- 

 nucleate parasite Opalina. Plere, where there is no need for digestive 

 activity, as the animal is immersed in already digested food-material, we 

 find a corresponding simplification of the nuclear elements, all of which 

 present the micro-nuclear karyokin^tically dividing structure. 



