Centrifugal Force upon Beetles' Eggs 



515 



The germ-band becomes narrower as development advances; its 

 posterior end pushes around that end of the egg and up on the 

 dorsal surface. The lateral folds gradually cover over the ventral 

 groove and the amnioserosal fold grows forward from the posterior 



— khbl. 



Fig. 9 Longitudinal section through an egg of C. bigsbyana four hours after deposition. |gf. J. = 

 germ-cell determinants, gn. = germ-nuclei copulating, khhl. = "Keimhautblastem." p. =lpos- 

 terior. v.m. = vitelline membrane, y. = yolk. 



end to meet the anterior fold (Fig. 5). The segmentation of the 

 germ-band and the lengthening of the entire embryo now pro- 

 gresses rapidly. The cephalic extremity extends almost to the 



