390 THE AMERICAN NATURALIST [Vol. XL V 



come the primordial germ cells (Fig. 4, C, G) and give 

 rise to the germ glands of the adult. The similarity 

 between this process and that described for Ascaris, Cy- 

 clops and Sagitta is obvious. 



Finally in chrysomelid beetles the primordial germ 

 cells are differentiated at a very early period (Hegner, 

 '09). At the posterior end of the eggs of Calligrapha 

 miiltipuitctata and allied species there is a disc-shaped 

 mass of granules which stain like chromatin. I have 

 called this the pole disc 

 (Fig. 5, A,gc. d). When 

 the cleavage nuclei reach 

 the periphery of the egg 

 they fuse with the super- 

 ficial layer of cytoplasm 

 everywhere except at 

 the posterior end; cell 

 walls then appear and a 

 blastoderm is formed, 

 gn- When the cleavage nu- 

 clei which reach the pos- 

 k h b i. terior end of the egg en- 

 counter the pole disc 

 * granules they gather 

 these granules about 

 v>m . them and continue their 

 migration (Fig. 5, B, 

 gc); cell walls are 

 formed, and they finally 

 come to lie entirely out- 

 side of the egg (Fig. 5, 



There are sixteen cells 



they take out of the egg 

 with them practically all of the pole disc granules (Fig. 

 5, C,pd.g). These sixteen cells divide to form thirtv-two; 

 in this division apparently one half of the granules con- 

 tained in each cell pass to each of the daughter cells (Fig. 



