194 



EMBRYOLOGY OF INSECTS AND MYRIAPODS 



germ band. As this depression deepens, the germ band moves toward 

 the posterior pole of the egg and withdraws into the yolk through the 

 depression until about half its length is immersed, the rest, including 



Fig. 116. — Libellula. Posterior end of egg. (cc) Cleavage cell, (ch) Chorion, (pr) 



Periplasm. 



the head lobes, remaining at the surface (Figs. 114:B, C). Therefore the 

 germ band of these species is only partially immersed, dilTering from some 

 other members of the order in this respect. 



ABC 



Fig. 117. — Calopteryx. Longitudinal sections. A-C, successive stages, (aw) Amnion. 

 {am. cav) Amniotic cavity, (ant) Antenna, {gb) Germ band, {hi) Head lobe, {ser) 

 Serosa. {From Brandt.) 



According to Brandt (1869), in Calopteryx the invagination continues 

 until the head shifts its position so that its vertex is directed toward the 

 posterior pole (Fig. 117). This is the immersed type of germ band. The 



