458 ROBERT W. HEGNER 



further course of development and where they may perhaps be 

 utihzed as food material after their disintegration" (p. 49). 



McClendon ('06) has likewise described a body embedded in 

 the cytoplasm of the egg of Myzostoma clarki which he derives 

 from the 'accessory cells,' which, as Wheeler ('96) has shown, 

 attach themselves to either pole of the oocytes. These 'acces- 

 sory cells' are really the 'Nahrzellen' of other authors. The 

 cleavage of the egg was not studied. Buchner ('10b) suggests 

 that this body described by McClendon and the 'nucleolus' of 

 Wheeler are identical and that through them the Keimbahn 

 may be determined. 



A metanucleolus has also been described by Hartmann ('02) 

 in Asterias glacialis. The germinal vesicle of the ovarian egg 

 possesses a 'Keimfleck' which contains all of the plastin and the 

 chromatin of the nucleolus. During the maturation the germinal 

 vesicle breaks down, the chromosomes escape from the 'Keim- 

 fleck' and the rest of this body becomes imbedded in the cyto- 

 plasm near the maturation spindle. 



Granules. Granules of various sorts which are segregated in 

 particular blastomeres have been noted in the eggs of various 

 animals and may have some relation to the Keimbahn. For 

 example, among the molluscs, Blochmann ('81) has described 

 the appearance of a group of granules in the early cleavage cells' 

 of Neritina which finally reach the velar cells. It is also probable 

 that Fol ('80) observed similar granules in the 16-cell stage of 

 Planorbis. In the same category, no doubt, belong the bodies 

 figured by Fujitas ('04) in the 4-cell to the 16-cell stages of Si- 

 phonaria lying at the vegetative pole, and the 'Ectosomen' de- 

 scribed and figured by Wierzejski ('06) in Physa. These granules 

 appear at the vegetal pole in the blastomeres of Physa during 

 the second cleavage; are at first imbedded in the entoderm mother 

 cells, but finally become localized in the ectoderm cells. They 

 periodically appear and disappear, and may, as suggested by 

 Wierzejski, represent only "eine besondere Erscheinung des 

 Stoffwechsels" (p. 536). 



Similarly in the rotifer, Asplanchna, Jennings ('96) has traced 

 a cloud of 'granules' from the eight-cell stage until the seventh 



