724 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Crocodiles, the first teeth develope from the jaw epithelium exactly like 
the placoid scales of Selachians. We have seen that the hinder teeth of 
Chamseleo are formed from the fusion of three small teeth. These are 
not all of the same size, the central one being larger and projecting. If 
we suppose the epithelium to proliferate further so as to form a rooted 
tooth instead of one fused to the jaw, we should have a tooth very similar 
to the molar of Dromatherium . 
It is of great importance to note that in Chamseleo and also in 
Hatteria a well-developed though functionless secondary germ exists. 
The ancestral forms must therefore have possessed teeth which were 
vertically replaced. It is the author’s belief that both Mammals and 
Theromorpha arose independently from an older polyphyodont Reptilian 
stock. 
Development of Pancreas in Ophidians.* — M. G. Saint-Remy 
remarks that, though numerous researches have been made on the 
development of the pancreas in recent years, no observer has recently 
studied that of Reptiles. In Tropidonotus natrix , at a stage corresponding 
to the chick of the fifth day, there may be seen the typical two ventral 
and one dorsal foundations of the organ. The ventral are absolutely 
isolated from the intestine, and arise from the hepatic duct as a mass 
of acini on either side ; their importance is slight as compared with 
the dorsal foundation. This, which is very large, communicates with 
the duodenum by a wide canal. In succeeding stages the three parts 
fuse into a single ovoid mass. Similar relations are to be seen in the 
Yiper. 
Gastrular Raphe of Triton alpestris.t — M. C. Van Bambeke finds 
that in urodele Batrachians, and especially in Triton alpestris , the median 
or dorsal groove (gastrular raphe), which in certain cases extends from 
the anterior boundary of the medullary folds as far as the hinder 
extremity of the primitive groove, is a vestige of this last ; it, indeed, 
is derived from the primitive blastopore or anus of Rusconi a short time 
after the commencement of gastrulation. It may be admitted, with 
0. Hertwig, that the median groove of Batrachians represents the line of 
suture along which the lips of the blastopore become juxtaposed and 
fused ; it is, therefore, comparable to what, in Ascidians, Amphioxus 
and Annelids, Hatschek has called the gastrular raphe. This groove 
fuses posteriorly with the still persisting part of the primitive groove. 
If the median really represents the line of suture of the lips of the 
blastopore we may say that the mesoblast on either side of the groove is 
a peristomial mesoblast, in Rabl’s sense. Like the facts described by 
O. Hertwig and Davidoff, the phenomena exhibited by urodele Batra- 
chians speak in favour of the theory of concrescence. 
Regeneration of Germinal Layers in Amphibia.:}: — Herr Bar- 
furth has made some observations on the subject which have convinced 
him that germinal layers of Amphibia are able to undergo regeneration ; 
there is a re-arrangement and re-differentiation of cells ; the regenerative 
power is greatest in the ectoderm. Mechanical injuries of the gastrula 
give rise to typical abnormalities and growths of definite structure. 
* Comptes Rendus, cxvii. (1893) pp. 405-6. 
t Bull. Acad. Roy. Belg., lxiii. (1893) pp. 710-26 (1 pi.). 
j Anat. Anzeig., viii. Erganz. Heft (1893) pp. 43-50. 
