GERM CELLS IN THE ARTHROPODA 117 



FIG. 37. Calligrapha. A. A germ cell of C. multipunctata 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. Longitudinal 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 ; k = killed portion of egg ; khbl. = keimhautbl astern ; p. = 

 posterior ; pgc = primordial germ cells ; v = vitellophags ; v.z. = 

 vesicular zone ; y. = yolk. 



