PTBO8OMA CLEAVAGE OF THE EGG. 



391 



be the case, however, only in the first stages of cleavage and to have no further 

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

 blastorneres. Many inner follicle-cells, as cleavage advances are, however, 

 found scattered between the blastomeres (Fig. 184 B, fz) and, as the distinc- 

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

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

 ( an also no longer be recognised, it is finally impossible to distinguish thefollicle- 

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



Ku;. 184. Sections of two germ-discs of 1'i/rosoma (diagrammatic after SALENSKV). 

 A, eight-celled stage ; /*, older stage, b, blastomeres ; do, food-yolk ; ds, covering 

 layer ; '/-. yolk-cells ; f, egg-follicle ; fz, immigrated follicle-cells ; ov, oviduct. 



SALKNSKV \vas unable to find follicle-cells showing the commencement of dis- 

 integration, this author concluded that the inner follicle-cells take part in the 

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

 with the Thaliacea (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 footnotes, pp. 420 and 421]. 



' 



