344 WHEELER. [Vo. III. 
1. There are no sufficient reasons for homologizing the 
embryonic envelopes of insects with the homonymous but 
dissimilar structures in Myriopods, Scorpions, and Perzpatus. 
2. There is no more than a superficial resemblance to speak 
for an homology between the dorsal organs of the Crustacea and 
the embryonic envelopes of Insects or between the dorsal 
organs of Crustacea and the homonymous structures in Insects. 
3. The dorsal organ of insects may be regarded as the neces- 
sary result of the rupture and absorption of the embryonic 
envelopes, and consequently as in no way related to such 
structures as the dorsal organs of Cymothoa, Limulus, etc. 
The process of envelope formation has been observed in 
numerous insects of all orders with sufficient accuracy to war- 
rant the assertion that all the pronounced types are connected 
by intermediate forms in fine gradation ; a fact which was long 
ago expressed by Kowalevsky (26). 
Diagrammatic longitudinal sections of embryos just after the completion of the 
envelopes. igure 3, Geophilus,; Figure 4, Calopteryx,; Figure 5, Aphis; Ligure 
6, Doryphora; Figure 7, Blatta; Figure 8, Bombyx. a. amnion; 5S. serosa; @s. 
amnion and serosa apposed; wv. ventral plate; fc/. procephalic lobes; y. yolk. 
If we suppose such a form as Calopteryx to present the origi- 
nal mode of embryo formation in the Hexapoda (and Paleontol- 
