GERM CELLS IN NEMATODES, SAGITTA 185 



In the eggs of Myzostoma, Wheeler (1897) found 

 that the nucleolus of the germinal vesicle does not 

 dissolve soon after it is cast out into the cytoplasm 

 during the formation of the first maturation spindle, 

 but remains visible at least until the eight-cell stage, 

 at which time it lies in the large posterior macromere, 

 a cell which "very probably gives rise to the entoderm 

 of the embryo." Later embryonic stages were not 

 studied. According to Wheeler "the nucleoli are 

 relegated to the entoderm cells as the place where 

 they would be least liable to interfere in the further 

 course of development and where they may perhaps 

 be utilized as food material after their disintegra- 

 tion " (p. 49). 



McClendon (19066) 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 (1896) has shown, attach them- 

 selves 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 (19106) suggests that this body described 

 by McClendon and the "nucleolus" of Wheeler are 

 identical and that through them the keimbahn may 

 be determined. 



Granules of various sorts have been noted in the 

 eggs of various animals which are segregated in par- 

 ticular blastomeres and may have some relation to 

 the keimbahn. For example, among the mollusks, 

 Blockmann (1881) has described the appearance of 

 a group of granules in the early cleavage cells of 



