- 
1886.] Entomology. 463 
is at first one-layered, and afterwards is composed of two layers, 
and then divides for the formation of the body-cavity. The pos- 
terior and anterior ends of the mesoderm-plate lengthen to form 
the mesoderm of the head and end of the abdomen. From these 
last portions of the mesoderm arises also the definite entoderm, 
viz., the epithelial covering of the mesenteron. The yolk cells 
thereupon disappear ; according to Grassi the figures quoted from 
Tichomiroff as well as from O. and P. Hertwig, in regard to the 
proof of the origin of the endoderm in the yolk cells can also be 
explained to agree with his views. The amnion and serous mem- 
branes are not separated in the bee, but form a single layer of 
cells. Grassi is inclined to trace the embryonal ‘membranes of 
insects phylogenetically from an especially modified dermal fold, 
which was inherited from the ancestors of the class; such a 
duplicature, suggests Emery, might be comparable to the mantle 
of many Entomostraca. 
According to Grassi the cerebral ganglia arise independently 
of the ventral chain, and is afterwards connected with it. The 
entire nervous system and, as far as could be observed, also the 
commissures arise directly from the ectoderm. The antennz are 
developed from the head plate (procephalic lobes) and are situated 
in front of the other appendages. A pair of cephalic appendages 
Previously observed by Biitschli, which only appear for a short 
time in front of the mandibles, soon disappear. Grassi considers ` 
them as homologous to the second antennz of Crustacea. e 
found abdominal appendages only exceptionally, and not on all 
the segments. The observations of Grassi on the mode of devel- , 
opment of the heart agree well with those of Korotneff on Gryl- 
lotalpa ; both uphold the hypothesis of Biitschli of the origin of i 
the vascular system from the residue of the segmentation-cavity, ` 
’. ê, the primitive body-cavity. The sexual organs originate as 
two mesodermal elongated streaks in the 4th-8th abdominal 
segments. 
The trachez arise very early; there are ten pairs of stigma 
atter found nine pairs of stigmata, but three pairs of malpighian __ 
tubes, „Grassi further ioner that the silk gaa and other m- 
se tions or “head-canals” found by him near the mandibles — 
d maxille are homologous with the trachez. fas gree 
c n case an entodermal origin for the antennal glands of the 
rustacea and the segmental organs (schleifenkanali) of annelids — 
Proved, then the first might be the homologues of the — 
