ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
31 
ferentiation. Secondly, as to the relation between the human primordial 
cranium and that of other Mammals, Jacoby thinks there is exaggeration 
in the common statement that the development of the primordial cranium 
gradually decreases throughout the series, and is at its minimum in 
man. He directs attention especially to the marked development of the 
“ parietal plates ” which in his specimen were strongly developed laterally 
and were also closed dorsally. Thirdly, as to the stapes, the author is 
very cautious, but believes in its relation to Reichert’s cartilage. He 
also notes that he found only a very narrow perichondrial layer between 
the distal ends of Meckel’s cartilages. 
Vitelline Body of Balbiani.* * * § — Herr H. Mertens has studied this 
much-discussed body in the ova of young mammals and birds, e. g. cat, 
rat, chick, pigeon. He finds that the term has been applied to two 
quite different elements. First, there is the attractive sphere, a rounded 
granular mass near the germinal vesicle, increasing in size as the ovum 
becomes more mature. Secondly, there are elements of nuclear origin 
found within the vitelline mass and consisting of chromatin granules of 
variable size. These are expelled from the germinal vesicle when it is 
young and active, and break up finally into vitelline granulations. 
Oogenesis in the Babbit and the Medullary Strands of the Ovary 
in Fox and Man.f — Dr. A. Biihler observes that a germinal epithelial 
cell in the rabbit divides by indirect cell-division into two cells, of 
which the one next the stroma becomes an ovum. This is enveloped by 
cells of the epithelium, and by the forward growth of the epithelium 
becomes ensheathod by the stroma. But when stroma and epithelium 
have not time to surround the ovum before new ova are produced, balls 
of ova and immigrant epithelial cells are formed ; at a later stage the 
epithelial cells are arranged around the ova, and the follicle rudiments 
so arising are received within the stroma. In man, similar facts were 
observed, excepting the mitoses in the germinal epithelium. 
In fox and man the Wolffian duct persists, for the most part oblite- 
rated, as a “fundamental strand” ( Grundstrang ) in the hilus ovarii. 
The medullary strands of the ovary are products of the epithelium of 
the same duct, which come into the closest relation with the growing 
follicles ; the tubules of the epoophoron have a similar origin. 
Anterior Extremity of Notochord in higher Vertebrates.^ — M. 
G. Saint-Remy finds that in Birds and Mammals the notochord ends 
primitively at the point of insertion of the pharyngeal membrane. It is 
only secondarily, and in consequence of the growth of epithelium, that 
it is displaced, and comes into relation with other points. The author 
refuses, therefore, to regard Seessel’s pouch as the end of the undeveloped 
notochord, and thinks rather, with Selenka, that the pouch has no morpho- 
logical significance, and is only a groove formed mechanically by the 
cephalic flexure. 
Origin of Sympathetic System.§ — Dr. G. Mazzarelli has investi- 
gated embryos of Pristiurus , Torpedo , liana, Tropidonotus , Zamenis , and 
* Arch. Biol., xiii. (1893, published July 1894) pp. 389-422 (1 pi.). 
f Zeitschr. f. wiss. Zool., lviii. (1894) pp. 314-39 (2 pis.). 
,% Comptes Rendus, cxix. (1894) pp. 567-9. 
§ Atti R. Accad. Lincei (Rend.), ccxci. (1894) pp. 269-73 (1 fig.). 
