340 WOOLFORD B. BAKER. 



by Minchin as being the chromatin mass at or near the center of a 

 "vesicular' nucleus, the precise nature of which not being 

 determined in the definition. There may or may not occur in 

 such a nucleus other granules of chromatin. If they do occur 

 they are always smaller than the central mass or endosome. 

 Some observers describe the structure as a body of homogeneous 

 character comparable to the nucleoli of other plant and animal 

 cells. Others say it consists of a matrix of plastin impregnated 

 with chromatin, arranged more or less in granules, and plays a 

 part in the formation of chromosomes (Berliner, 1909; Haase, 

 1910; Schiissler, 1917; Hartmann, 1919, 1921). Still others, 

 Keuten (1895) compare it with the centrosome and central spindle 

 of diatoms and speak of it as the "nucleolo-centrosome." 

 Schaudinn (1896) thought he had demonstrated this to be the 

 nature of the endosome in Oxyrrhis when by placing the animal in 

 dilute sea-water the endosome migrated from the nucleus and 

 functioned as an extranuclear centrosome. Hall (1924), after 

 critical study of Oxyrrhis, thinks Schaudinn's supposed endosome 

 was a small food mass. Steuer (1904) describes a "nucleolo- 

 centrosoma" in the center of the nucleus of Eutreptia. In the 

 work of TschenzofT and in the general work of Doflein the body is 

 spoken of as the "Binnenkorper," which term is quite non- 

 committal both as to structure and function. 



The question of the presence of a centriole in the endosome has 

 also been the subject of much discussion. Schiissler (1917) 

 believes that both nuclear components are located in the endo- 

 some of Scytomonas , and that from this type as a starting point all 

 degrees of differentiation of the kinetic and generative com- 

 ponents may be found. Belar (1916) figures definite centrioles in 

 the endosome of Astasia, tracing them through their entire cycle. 

 In Rhynchomonas, he describes a centriole which passes from the 

 karyosome to the nuclear membrane where it divides. In the 

 same paper (1916) he concludes that "the basal body of Flagel- 

 lates is doubtless a centriole." 



A good summary of the relation between the kinetic and 

 generative components of the nucleus, bearing upon the problem 

 of the endosome, is to be found in the work of Hartmann (1918) 

 and of Jollos (1917): 



