Plate XX I II 



3 



Segmentation of the egg of Miastor atnericanus, after HEKNER (1914). 



1, two segmentation nuclei (t'..)> dividing polar nucleus (/>..), Plar plasma 



(germ-cell determiner, />./>.) a "d group of nurse-cells (n.c.). 



2, rather later stage with one primordial germ-cell (p.g.c.}, nuclei undergoing 



chromatin-diminution (r.w.), and clumps of cast-out chromatin (c.r.). 



3, 4, early and later blastoderm stages with two and four primordial germ-cells. 



