NUCLEI AND KINETIC ELEMENTS 



63 



in the form of more or less regular chromomeres uniformly dis- 

 tributed in the nuclear space (Euglena type, Fig. 25), or more or 

 less compactly aggregated about the kinetic element (many species 

 of Endamoeba, various flagellates, Coccidia and Myxosporidia, etc.). 

 Or, finally, the chromatin may be in the form of relatively large 

 granules collected in a zone just within the nuclear membrane 

 {e. g., Pelomyxa), or in fine granular form may make up the chief 

 part of the nuclear membrane {Vahlkampfia Umax, Fig. 26). 



Fig. 26.— Division of ama-ba. -4. to /, successive stages in division (promitosis) of 

 Vahlkampfia Umax; J to L, mitosis in Endamceba coli. (Original.) 



A peculiar and most unusual type of vesicular nucleus is present 

 in Nodiluca viiliaris and has the superficial appearance of a massive 

 nucleus. Two distinct types of structure have been described, one 

 by Doflein, the other by Calkins, and the descriptions differ so widely 

 that it is difficult to recognize them as pertaining to the same 

 organism. According to Doflein, the nucleus belongs to the massive 



