195 Embryology. 745 
A Contribution to Insect Embryology.'—Under this title Mr. 
W. M. Wheeler presented to the Faculty of Clark University a 
dissertation that demonstrates the high ideals attained in Biological 
work at that institution. 
It is sufficient indication of the character of the work to say that it 
is worthy of the elegant illustration it has found in the Journal of 
Morphology. 
It is chiefly a study of gastrulation, formation of embryonie mem- 
branes, nervous system and reproductive organs in the locust, Xiphi- 
dium ensiferum Scud., though a much broader view is given by illus- 
trations drawn from the author’s work upon numerous other insects, 
notably the Orthoptera. 
The eggs of this insect are laid in the willow galls produced by a 
Cecidomyia. They were hardened in water heated to 80? C. and after- 
wards kept in 70 per cent aleohol for weeks or months to allow the 
yolk to shrink from the chorion. Surface views and sections were then 
prepared by methods but little modified from those of Graber and of 
Patten. 
The blastopore extends nearly the whole length of the germ band 
and is bifurcated posteriorly in a way strangely suggestive of the 
"sickel" of the chick embryo. It closes from each end toward the 
middle or future baso-abdominal region and by a process of “slurred” 
invagination thus gives rise to the mesentoderm. . 
In almost all other Orthoptera there is also, the author shows, an 
invaginate gastrula. 
Later a most remarkable migration of the embryo takes place and 
complicates the difficult subject of the complex embryonic membranes. 
Lying first upon the ventral surface of the egg, with its head 
toward the anterior and sharper end of the egg, the embryo actually 
sinks down into the yolk and by bending comes to lie upon the dorsal 
side with its ends reversed, its head toward the posterior or larger end 
of the egg. The appendages having meanwhile become so well devel- 
oped that the leaping legs are distinguishable from the others, the 
embryo moves back into its original position upon the ventral side of 
the yolk, bending back so that it lies as at first. This second migra- 
tion, however, is not through the yolk but upon its surface, over the 
osterior end of the egg. 
: hese peculiar Pisa of the embryo, which the author would 
embrace under the term “ blasto-kinesis," may, he thinks, be explained 
as of physiological use. He first shows that the primitive winged 
* Journal of Morphology, Vol. VIII, No. 1, 1893. 
