No. 2.] BLATTA AND DORYPHORA. 341 
trula, which has retained its ability to form entoderm only at the 
oral and analends. Putting this construction on the gastrula, 
it is, of course, easy to reduce the germ layers of insects to the 
Sagttta pattern. 
Kowalevsky’s results on JZusca have been corroborated as 
far as the posterior Extodermanlage is concerned by Biitschli 
(8); while his main results on Hydrophilus have been con- 
firmed by Heider (19). 
According to Heider, the tube formed by the closing gastrula 
flattens out, and the half of it immediately below the ectoderm 
becomes mesoderm, afterwards splitting into the somatic and 
splanchnic layers; while the other (inner) half becomes the 
entoderm which spreads apart to form two bands, one on each 
side applied to the part of the mesoderm inclosing the ccelomic 
cavity. Subsequently the proliferating edges of the bands 
unite ventrally and dorsally to complete the mesenteron. 
A comparison of my account of Doryphora with Heider’s 
account of Hydrophilus will show that I differ from Heider on 
one point only. I claim that all the entoderm between the oral 
and caudal widenings of the blastopore is not derived from the 
inner cells of the gastrular depression, but grows in from the 
ends of the body. I do not deny that the entoderm may arise 
in Hydrophilus (and possibly in Doryphora) in the manner 
described by Heider, ze. from the inner layer of cells of the 
gastrular tube when it flattens out and breaks down, but I 
would regard the process as confined to two very small areas, 
one being stomodzeal, the other protodzeal. 
Heider’s figures are undoubtedly correct and correspond in 
every way to sections through Doryphora embryos in corre- 
sponding stages. Unfortunately, he has not noted with any 
precision the plane of section.of the different preparations 
figured. Starting with his Plate II., his figures may be inter- 
preted in harmony with Doryphora, thus :— 
Figure 23 is exactly like my Fig. 88, omitting the degenerating 
nuclei, and I should interpret it in the same way as Heider. 
My section passes through the caudal plate of the embryo; 
Heider’s passes “durch den Abdominaltheil,’’ which is indefi- 
nite. In Figs. 24 and 25 I can see no entoderm, but merely 
the apposed splanchnic and somatic layers of mesoderm between 
the lateral ends of which the coelomic cavities are about to 
