PYBOSOMA CLEAVAGE OK THE BGG. 



39] 



be the case, however, only in the first stages oi cleavage and bo have do further 

 significance, since the follicle-cells, as it appears, do not remain inside tlie 

 blastomeres. Many inner follicle-cells, as cleavage advances arc, however, 

 found scattered between the blastomeres (Fig. LSI B,fz) and, as the distinc- 

 ion of size between the two kinds of ceils disappears when the blastomeres 

 divide further, and the original histological character of the inner follicle-cells 

 can also no longer be recognised, It is finally impossible to distinguish thefollicler 

 cells from ilit- actual germ-cells or blastomeres. For this reason, and because 



Pig. 184. Sections of two germ-discs of Pyrosoma (diagrammatic after Salensky). 



I. eight-celled stage; II, older stage, b, blastomeres; do, food-yolk ; ds, covering 



layer ; dz, yolk-cells ; i . egg-follicle ; fz, immigrated follicle-cells : ov, oviduct. ',\ 



Sai.knskv was unable bo find follicli 



si] 



c-cells sin 



iwing the commencement of dis- 



integration, this author concluded that the inner follic 



lis i ake part in t he 



formation of the embryo, a view resembling that held by him in connection 

 with the Thaliacca (p. 420). We consider it to be more probable that the 

 embryo here, as in the Thaliacea, is produced solely by the blastomeres, and 

 that the follicle cells which wander in between the blastomeres undergo final 

 disintegration. [See footuotes, pp. 420 and 421]. 



