ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
605 
The cephalic duct forms hut a small part of the hepatic tissue. The 
buds of the two ducts unite in such a way that the liver gradually takes 
on the form of a single organ which surrounds the venous sinus. 
The gall-bladder is developed from a diverticulum of the caudal 
canal. Once formed the liver loses most of its connections with the 
caudal canal, and there is then formed the plexus of excretory ducts 
which brings the hepatic mass into relation with the cephalic canal, 
which contributes so little to the development of the organ. The caudal 
canal persists as the cystic-enteric duct. 
The author has been able to study three human embryos ; he finds 
that the mode of development of the liver is analogous to that which he 
has observed in the Chick ; but the constriction which separates the 
canals from the duodenum begins early, and so causes the length of the 
ducts. 
Like Goette, Felix finds that the pancreas of the Chick arises from 
three foundations, one dorsal and two ventral ; all three are diverticula 
of the anterior part of the intestine. The same seems to be true of Man, 
save that the ventral diverticula fuse. 
Development of Mustela ferox.* — Dr. A. Robinson has some notes 
on the early stages of development in the Ferret. He was able to see 
two primitive germinal layers, and he points out that if it is right to 
call the inner one hypoblast the remainder of the cellular wall with 
which it is continuous is also hypoblast ; in this case the blastocyst is 
essentially a large yolk-sac which bears upon one pole a small area of 
epiblast. If this be so, the ovum of the Ferret, as well as those of the 
Rat and Mouse, bear testimony to the descent of the Mammalia from a 
large-yolked protamniote ancestor, for it shows during its early stages 
the typical features of all comparatively large-yolked vertebrate ova. 
No trace could be seen of any difference in thickness of the margin of 
the germinal area such as would indicate the existence of a widely open 
true blastopore, nor was there any trace of such an aperture within the 
area itself. 
Development of Mammalian Dentition.f — Dr. W. Leche begins an 
important essay with some criticisms and cautions in reference to some 
of the numerous recent publications on the dentition of Mammals. 
Some of these seem to him to be unduly rash. He indicates what is the 
safe method of investigation. 
By means of continuous serial sections the author has for many 
years been accumulating facts in regard to the development of the teeth 
and the relations of the two dentitions. He begins with the hedgehog. 
The formula of its normally persistent dentition is — 
i. 1, i. 2, d i. 3 ; C ; d. p. m. 2, p. m. 3, p. m. 4, m. 1-3 
i. 2, d. i. 3 ; d. C; d. p. m. 3, p. m. 4, m. 1-3* 
The functional replacing teeth are — 
i. 1, i. 2, C, p. m. 3, p. m. 4 # 
i. 2, p. m. 4 ’ 
* Anat. Anzeig., viii. (1893) pp. 116-20 (2 figs.), 
f Morphol. Jahrb., xix. (1892) pp. 502-47 (21 figs.). 
