116 
36) Zacorsxy, P., Mém. de |’ Acad. de sc. de St. Pétersbourg. T. VII. 
1822. S. 288. — Sog. Verdoppelung der Vena cava inferior. Ver- 
einigung zu dem unpaaren Stamm in der Höhe der Arteria mesen- 
terica superior. Verbindungsast scheint nicht bestanden zu haben, 
also Verhalten wie Fig. 2. 
37) Zaatser, Arch. Neerl. Tom. VII. S. 451. Mit 1 Tafel. 
38) ZanpER, Ueber Verdoppelung der unteren Hohlvene. Verein f. w. 
Heilkunde zu Königsberg i. P., Sitzg. vom 21. März 1892. — Z. 
zählt 29 Fälle, es muß jedoch davon einer abgezogen werden, den 
er vermutungsweise hinzugezählt, weil ihm die betr. Abhandlung von 
Eppineer, Mitt. d. Vereins der Aerzte in Steiermark 1889, Graz 1890, 
S. 144 nicht zugänglich war. Sie betrifft eine doppelte Vena cava 
superior. 
Nachdruck verboten. 
Observations upon the Development of the common Ferret, 
Mustela ferox. 
By Arraur Ropınson, MD., 
Senior Demonstrator of Anatomy at the Owens College, Manchester. 
With two figures. 
In Volume XXXIII, Part 3 of the New Series of the Quarterly 
Journal of Microscopical Science I attempted to show that the com- 
monly accepted explanation of the constitution of the mammalian 
blastodermic vesicle was incorrect. 
The basis of the attempt was the result of a series of observations 
made upon the young ova of rats and mice. The observations revealed 
the fact that, in the ova of rats and mice, a segmentation cavity and 
an archenteric space developed successively and that the formation 
and extension of the latter, in the midst of the hypoblast, were co- 
incident with the diminution and disappearance of the former, from 
between the epiblast and hypoblast. 
Evidently therefore the early stages of ovular development in 
these mammals, at least, does not deviate from the ordinary type of 
vertebrate ontogenetic evolution, and it seemed probable that between 
them and more aberrant mammalia some connecting link might be 
discovered which would explain the formation and evolution of a 
blastodermic vesicle such as that usually described, i. e. a blasto- 
dermic vesicle developed at the close of the segmentation period by 
a UL 
