ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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the great omentum ; others may be seen in the course of a capillary, or 
at the end of a small artery or vein. Sometimes one may meet with 
them on the course of a capillary loop which connects the artery with a 
vein. In this case the artery is continued insensibly into the capillaries 
of the plexus. The cells and the vaso-formative plexuses, and the 
points of growth of the vessels play a part in the formation of the blood, 
for they give rise to blood-corpuscles. These are of an intracellular 
nature, and even of an intra-protoplasmic ; they do not contain any 
nucleus. The author has found it impossible to make certain of the 
origin of the vaso-formative cells ; it is not possible to assume that they 
are derived from the lymph or from the connective tissue, for there are 
too great differences between them and the lymphatic or connective cells. 
In character they approach the points of growth of the blood-vessels. 
It follows that the blood-corpuscles of Mammals have the same origin 
as the blood-vessels. 
Development of the Hepato-enteric Diverticula of the Axolotl, and 
of the Peritoneal Cavity of Mammals. * — M. A. Brachet finds that 
in the Axolotl two hepato-enteric blind diverticula of the coelom fuse 
to form the hepato-enteric cavity of the adult, but that the right 
diverticulum takes a larger share than the left. In the Chick, as shown 
by Duval, the right sac alone forms the cavity of the adult. In the 
Rabbit the right diverticulum is alone developed. The hepato-enteric 
diverticulum causes the division of the primitive dorso-ventral mesenteric 
septum into two parts. The right is the meso-lateral, and the left con- 
tains the digestive tube. The former will ultimately give rise to the 
dorsal ligament of the liver, while the left becomes divided by the diges- 
tive tube into three parts. It is very difficult to determine in the 
young embryos the respective limits of the future stomach and duodenum, 
but it is probable that the diverticulum is produced in the plane of this 
boundary, and, in a general way it may be said that the dorsal meso- 
gastrium arises from a fold of the primitive dorsal mesentery ; that the 
meso-duodenum is formed by the whole of this mesentery ; that the ven- 
tral meso-gastrium or gastro-hepatic ligament also arises from the fold 
of the primitive ventral mesentery, while the duodeno-hepatic liga- 
ment is formed by the unfolded part of the primitive ventral mesen- 
tery. The author comes to the conclusion that the mesenteries of the 
Rabbit and of the Axolotl are not exactly similar. 
Young Monotremes.t — Prof. J. T. Wilson describes and figures a 
young example of Ornithorliynchus anatinus , which appears to be the 
smallest and youngest specimen that has yet been under observation. 
Some details as to the external parts are given, and it is urged that the 
epithet of “ horny ” is not one which is correctly given to the beak of 
the Duckbill. 
Messrs. J. P. Hill and C. J. Martin J have an abstract of their paper 
on two embryos taken from the intra-uterine egg of Platypus. Owing 
to the relatively very early great lateral extension of the mesoderm, and 
from the presence of a very distinct volk-containing endoderm, the vesicle 
of the Platypus embryo of this stage is regarded as transitional between 
* Arch. Biol., xiii. (1895) pp. 559-618 (4 pis.). 
t Proc. Linn. Soc. N.S.W., ix. (1895) pp. 682-90. J Tom. cit., pp. 783 and 9. 
