90 Walter E. Dandy. 
ventral projection of the dorsal aorte. These are no doubt accentu- 
ated by post-mortem shrinkage. The opening of the foregut is strad- 
dled by two prominent ridges which unite above into a large ventral 
bulging, represented by the overlying ccelom, and pericardial cavity 
with the enclosed heart, respectively. 
The foregut is present in 32 sections, representing a length of 320 
microns. It ends blindly anteriorly and is separated by mesoderm from 
the bueceal cavity which is forming by an invagination of ectoderm. 
There is however no bucco-pharyngeal membrane. One small pharyn- 
geal pouch is present on each side below the first and only complete 
aortic arch. These pouches are continuous ventrally and unite to 
form a ventral pouch. ‘There is no contact with the outer ectoderm, 
although the mesoderm separating them is considerably thinner than 
elsewhere. 
The hindgut is a blind somewhat oval, dilated pouch, 120 microns 
in length by sections, but on account of the dorsal kink of the embryo 
and the consequent partially longitudinal plane of the sections, the 
actual length is somewhat greater. The allantois arises from the 
ventral surface of the hindgut. It passes from the embryo into the 
bauchstiel in company with and between the umbilical arteries. 
After the union of these arteries, it takes its position between the 
arterial and venous sinuses (Plate VI) and bends at almost a right 
angle to conform to the direction of these sinuses and the bauchstiel. 
At this latter point it divides into a short stub measuring about 40 
microns and a much longer branch. The terminus of each branch 
may be seen in Figs. 8 and 9. The allantois is lined by a single 
layer of cubical epithelium; it maintains a lumen to the Bera of 
division, from which it consists of a solid core of cells. 
No liver or thyroid anlage has made its appearance. No cloacal 
or bueco-pharyngeal membranes can be distinguished. 
Notochord. With the exception of the very posterior tip which 
is entirely free for a distance of three sections, the notochord is 
everywhere fused with and apparently an integral part of the ento- 
derm. Posteriorly it is very conspicuous as a relatively large and 
very compact knob of deeply staining cells on the dorsal wall of the 
hindgut. This sharply differentiated mass invaginates. into the 
ectoderm, with which is it not here united (Fig. 6). It gradually 
