STUDIES ON GERM CELLS 



405 



-pd-g. 



R 



-gca 



H 



PSC 



X- p 



I 



Fig. 8 Calligrapha (from Hegner, '09a, '09b, '11a). A, a germ cell of C. multi- 

 punctata shortly after being cut off from the egg. B, division of a primordial germ 

 cell. C, longitudinal section through egg of C. bigsbyana at blastoderm stage; 

 the posterior end was killed with a hot needle just after deposition. D, longi- 

 tudinal section through uninjured egg at same stage. E, two ectoderm cells 

 (e), two mesoderm cells (m), and two germ cells (g.c.) from an egg three days old. 

 F, germ cell during migration into the embryo (three days old). G.H.I, longi- 

 tudinal sections through eggs centrifuged for one hour, two hours and four hours 

 respectively, bl, blastoderm; g.c.d, granules of pole-disc; A-, killed portion of 

 egg; khbl, keimhautblastem; p, posterior; pgc, primordial germ cells; v, vitello- 

 phags; t'.?, vesicular zone; y, yolk. 



