No. 382.] REVIEWS OF RECENT LITERATURE. 797 
before or during the invagination of the proctodzum, as two pairs of 
depressions in the ectoderm of the anal segment. 
Biirger describes the formation of the midgut, or mesenteron, in 
detail. The vitellophags left in the yolk when the segmentation 
cells are migrating to the surface to form the blastoderm, in the 
later stages of development arrange themselves on the surface of the 
yolk as a continuous epithelium immediately inside the entoderm. 
This vitellophag layer, however, forms no portion of the definitive 
midgut wall, but disintegrates towards the close of embryonic life, 
just as the scattered vitellophags disintegrate in other insects. 
Biirger’s account of the nervous system of the Chalicodoma embryo 
is mainly valuable as a confirmation of the observations of Heider, 
Wheeler, and Viallanes on other insects. Carrière and Birger 
regard the frontal ganglion as the first segment of the brain, and 
the labrum as its pair of appendages. Their interpretation of the 
remaining head segments is the same as that of the above-mentioned 
authors. The ventral nerve chord is derived from neuroblasts similar 
to those found by Wheeler in Doryphora. The ganglionic cells budded 
off from the neuroblasts are not in regular rows as in the Orthoptera 
(Xiphidium, é.g.). The account of the origin of the Mittelstrang is 
unsatisfactory. Bürger agrees with preceding writers in deriving the 
ganglia of the sympathetic nervous system from the dorsal wall of 
the stomodeum. The “ganglia allata” which Heymons discovered 
in Forficula arising from a pair of invaginations near the base of the 
maxilla and subsequently moving around and uniting on the dorsal 
surface of the stomodzum, are probably not ganglia at all, if certain 
large structures found by Biirger in corresponding positions in the 
bee should prove to be homologous with the bodies observed by 
Heymons. 
The development of the body-cavity (schizocceele) is traced by 
Birger, together with the portions of the walls of the ccelomic sacs 
that give rise to the heart, pericardial septum, pericardial fat-body, 
the main mass of the corpus adiposum, the ventral and dorso-ventral 
musculature. The heart is formed from two rows of cells (cardio- 
blasts), which move towatds each other around the yolk and finally 
unite to form a tube in the mid-dorsal line. The deutocerebral is 
the only head segment that contains a pair of mesoblastic somites 
with distinct coelomic cavities. 
Carrière finds the first traces of the reproductive organs in embryos 
with the full number of segments and the appendages beginning to 
bud out. They appear as large cells in the walls of the mesoblastic 
