ATYPICAL MITOSIS AND OTHER NUCLEAR PHENOMENA 189 



tissues are an important cause of certain phenomena of cell growth and 

 multiplication. 



Karyosome Nuclei. — Numerous peculiar types of nuclear organi- 

 zation and behavior are known in the lower organisms, notably among 

 flagellates and Protozoa.-" Of these types one of the most prevalent is 



%•' 





^"-4-^ 



Fig. 110. — Mitosis in Oxyrrhis marina. 1, living individual, showing two flagella and 

 two food bodies. 2, 3, and 4 show the paradesmose between the diverging centrioles. 

 6, endosome elongated and about to divide. 6, early telophase. 7, 8, fission in progress. 

 {After Hall, 1925a.) 



that in which the nucleus contains a large, deeply staining body known as 

 the karyosome, or endosome ^^ It may contain the only highly chromatic 

 substance in the nucleus at certain stages, but critical studies have shown 

 that the chromosomes, like those in ordinary nuclei, develop in the 

 surrounding region (Figs. 110, 111). The karyosome usually reacts 

 negatively in the Feulgen test,-^ but it may still be concerned in the 

 changes in chromaticity of the chromosomes (c/. p. 119). Ordinarily 



20 Pqj. general accounts of the nuclei of Protista, see M. Hartmann (1911), Minchin 

 (1912), Doflein (1916), Calkins (1926) and Belaf (1926). 



^^ Minchin's term endosome is probably used more widely now than karyosome 

 (Hartmann). Other terms are Binnenkorper (Doflein) and nucleolo-centrosome 

 (Keuten). Much of the confusion in the older literature on this subject has been 

 clarified by recent work; see especially Belaf (1926), Hall (1925a) and Hall and 

 Powell (1928). 



22Reichenow (1928), Roskin and Romanova (1928). 



