XII] 



EMBRYOLOGY 



231 



Vitellophags. While the blastoderm is being formed, certain 

 cleavage cells migrate inwards. These increase by division to 



G 



H 



K. 



Fig. 109. Ten stages in the embryonic development of Calopteryx. Lateral view, 

 dorsal surface to the left, ventral to the right. A. Formation of ventral 

 plate. B-D. Stages in the invagination of the embryo. E-G. Formation 

 of appendages. H-K. Rupture of amnion, and reversion of embryo towards 

 its final position, ab abdomen; abd abdominal segment; ac amniotic cavity; 

 am amnion; as union of amnion and serosa; at antenna; 6 lateral border 

 of ventral plate ; bl blastoderm ; bp blastopore ; c cap or pedicel ; ch chorion ; 

 cl cephalic lobe; emb embryo; fg stomodaeum; hd head; Jig proctodaeum; 

 lj-l a legs ; Ibr labrum ; md mandible ; mx 1 first maxilla ; mx z second maxilla 

 (labium); se serosa; vp ventral plate; yk yolk. After Brandt. 



