No. 3.] THE PROTOZOA AND METAZOA. 747 



A similar central nuclear body has been described by Schau- 

 dinn in Amoeba crystalligera. With high powers he was able 

 to make out a certain alveolar ("wabige") structure of the 

 "nucleolus" ("achromatic body"), and, in addition, he occa- 

 sionally found in it a granule or granules which stained with 

 chromatin dyes. He included all of these granules in the 

 nucleolus. The chromatin undergoes no preparatory changes 

 before division, and the nucleus divides first, the deeply stain- 

 ing granules having meantime disappeared. 



Schaudinn considers this a confirmation of F. E. Scliultze's earlier 

 description of the division of Amoeba as amitotic, although he seems to 

 realize the significance of the nucleolus when he says : " Der als Nucleolus 

 bezeichnete Theil des Kerns scheint bei Durchschniirung des Kerns, wie Fig. 

 \\ b vl. Ill b zeigen, die Hauptrolle zu spielen " (p. 1035). The presence of 

 granules within the " nucleolus " is interesting, and may be taken as a pos- 

 sible indication of an early stage in the differentiation of a centrosome. 



The intra-nuclear " achromatic body " plays a more impor- 

 tant role in the nuclei of EiiglypJia, Spiroc/iona, and Kcntro- 

 cJiona. In the former the bodies at the poles of the spindle 

 are considered by Schewiakoff the same as the " Polkorperchen " 

 (centrosomes) of metazoan nuclei. Their history is not clearly 

 made out, but his description seems to indicate a nuclear 

 origin, though he himself draws a different conclusion. His 

 account is as follows : " The polar cytoplasm develops radial rays 

 (' Polstralen ') which converge at the ' Polkorperchen ' (pole- 

 plate) in a small invagination of the nuclear membrane. At 

 the same time spindle-fibers make their appearance inside of 

 the nucleus, and he concludes, therefore, that the ' Polkor- 

 perchen ' is derived from the pole-rays by the coalescence of 

 the cyto-microsomes lying in them. There is no mistaking 

 Schewiakoff's meaning ; the pole-bodies are derived from the 

 cytoplasmic granules. There are, however, some significant 

 features in his account of the division which throw consider- 

 able doubt on this inference. In the first place, at the time 

 when the spireme is well formed, and just before the formation 

 of the ' Polkorperchen ' the so-called ' nucleolus ' disappears. 



There is, in reality, no occasion for using it at all, for the meaning is much better 

 expressed by the terms "chromatic body" (or karyosome) and " achromatic body." 



