EMBRYONIC ENVELOPES, DORSAL ORGANS, BLASTOKINESIS 55 



hh. Yolk between amnion and serosa; lacking in some 

 cases at the head end before final revolution {i.e., 

 germ band immersed). 

 i. Embryo completely immersed shortly before fusion 



of amnion and serosa (Fig. 193) 



V. Anoplura, Mallophaga, Plecoptera {Ptero- 

 narcys), Thysanoptera, Heteroptera {Pyrrhocoris, 

 Rhodnius), Homoptera in part, Corrodentia, 

 Orthoptera in part {Stenobothrus), Coleoptera in 

 part (Photurus), Orthoptera in part 

 a. Embryo immersed except at head end (Fig. 117C). 

 IV. Homoptera (in part), Ephemerida, 



Odonata, in part 

 gg. Amnion and serosa do not fuse shortly before revolution; 

 tubular secondary dorsal organ normally lacking. 

 h. A fold of the amnion forms a temporary dorsal closure 

 (Fig. 311). 

 i. Embryo wholly immersed in the yolk; amnion in 

 some cases at least does not completely cover the 

 ventral face of the embryo until completion of 



the serosa VI. Lepidoptera 



a. Embryo not immersed (Fig. 255) 



VII. Tenthredmidae {Hyloioma), Coleoptera in 



part {Leptinotarsa, Clytra, Chrysomela, Euryope, 



Corynodes, Bruchus, Calandra, Brachyrhinus) 



hh. No fold of the amnion forms a temporary dorsal 



closure. .VIII. Siphonaptera, Nemocerous Diptera 



Of the groups given in the foregoing table we may recognize several 

 types of which the following are more or less distinctly marked. Some 

 aberrant forms are omitted. 



I. Ventral face of the embryo not covered by a membrane (Fig. 74) 



Myriapoda, Collemhola, Diplura 



II. Membranes not completely closing over the ventral face of embryo (Fig. 109). 

 Thysanura 



III. Serosa and amnion fully developed, fusing either ventrally or at head end just 



before revolution; secondary dorsal organ formed; germ band superficial 



Orthoptera, Eutermes, Dermaptera, Neuroptera, Trichoptera, Coleoptera (in 

 part), Heteroptera (Corixa), Odonata in part 



IV. Like III but germ band is immersed except at the head end 



Odonata, Ephemerida, Emhiidina, Homoptera (in part) 



V. Like IV but head is also immersed until just preceding revolution 



Anoplura, Mallophaga, Corrodentia, Thysanoptera, Homoptera (in part), 



Heteroptera (in part) 

 VI. Amnion and serosa fully developed, although in some cases at least, the amnion 

 does not form until the serosa is completed; envelopes do not fuse at the head 

 end just before revolution; germ band immersed; no dorsal organ; a part of 



the amnion forms a provisional dorsal closure Lepidoptera 



VII. Serosa and amnion fully developed and do not fuse at the head end just before 

 revolution nor do they rupture at revolution; germ band not immersed except 



