340 WHEELER. [Vot. III. 
the more primitive and Doryphora the more modified method 
of germ-layer formation. I would note in this connection that 
the mesoderm of A#/at¢ta is formed in a manner strikingly sim- 
ilar to that observed in Perzpatus by Kennel (24). Reference 
to the diagrams, Figs. 1 and 2, will make further remarks on the 
relation of the two modes of germ-layer formation in A/atta and 
Doryphora unnecessary. 
Kowalevsky, Hatschek, Patten, Heider, and Biitschli have 
published observations which have a decided bearing on the 
method of entoderm formation in Doryphora. 
Kowalevsky (26) claimed in his epoch-making work that in 
Hydrophilus the two longitudinal bands of entoderm are derived 
by delamination from the splanchnic mesoderm, which he erro- 
neously supposed to originate from the primitive mesodermic 
layer by an incurling of its lateral edges. As we have seen, 
Cholodkovsky also claims that the entoderm of 4/a/za is derived 
by delamination from the splanchnic mesodern. 
Hatschek (18) figures in Bombyx chrysorrhea a large mass 
of entoderm cells immediately beneath the stomodzeum. This 
mass may be compared with either the anterior or posterior cell 
masses of a similar nature in Doryphora. 
Patten (38) figures a cluster of several huge entoderm cells 
attached to the stomodzeum of WVeophalax (Pl. XXIV. C. Fig. 
36), and in a more recent paper (39) he has figured similar cells 
in the same position in the embryo Acz/zus. 
Two recent papers on J/usca, one by Kowalevsky (27) and 
one by Biitschli (8), contain accounts of a method of entoderm 
formation very similar to that observed by me in Doryphora. 
Kowalevsky finds that the entoderm originates in two widely 
different points, anteriorly at the inner end of the stomodzum 
and posteriorly at the inner end of the proctodzum, from some 
of the cells of the gastrular invagination. The mass of entoderm 
at either of these places forms a watch-glass-shaped body with 
its concavity applied to the yolk. From the lateral edges of 
each mass the entoderm cells proliferate to form two bands, 
each of which unites with the one on the same side growing 
from the opposite direction. By a dorsal and ventral growth of 
the edges of the two bands the entoderm envelops the yolk and 
thus completes the mesenteron. Kowalevsky also regards the 
entoderminic invagination in insects as a greatly elongated gas- 
