92 
ON THE PHYSIOGNOMY OF SERPENTS. 
by several physiologists, has been regarded by others 
as analogous the Chorion.^ Probably this tunic is com- 
posed, as in the eggs of Tortoises, of two lamellae, the ex- 
terior of which, containing the bloodvessels, may perhaps be 
compared to the chorion of the embryon in mammifera, 
while the interior is the true allantois.! The embryon it- 
self is shut up in a serous membrane, the amnion. The 
canal of the vitellus enters the small intestine near the py- 
lorus ; but the umbilical opening is not always found oppo- 
site to that region: in the Trigonocephalus atrox, where it is 
near the anus, the canal of the vitellus is obliged, in order 
to enter the duodenum, to mount in the interior of the ab- 
dominal cavity the whole length of the intestines. 
The number of young which Ophidians produce at a 
single deposition of eggs, differs considerably in the different 
species. I have observed in several Calamarise not more 
than ten ; some Colubri lay from twenty to twenty-five ; 
I have found thirty and more in the Trigonocephalus atrox, 
and it is said that our Ringed Snake lays as many as 
forty. On opening the belly of a pregnant snake we see 
the eggs, impacted one against the other, and arranged in 
masses, occupying in all their length the oviducts, which 
then resemble a necklace. The embryon has all its tegu- 
ments colourless, and the eyes extremely developed and 
salient ; the head is rounded, the muzzle short, sloping, 
and resembling that of a dolphin or of a fowl. In pro- 
portion as the foetus is developed, so much nearer does its 
form approach to that of the perfect animal. To disengage 
itself from its prison, the young snake, probably by the 
power of its movements, ruptures the tunics which inclosed 
it. This operation it can easily perform when the coats are 
membranous, as in the viviparous species ; but it must require 
great efforts to burst the coriaceous envelope of the true 
egg : three or four longitudinal rents, near the end of the 
^ It is for this reason that some deny the existence of the allantoid 
in the eggs of the Ophidians, while others maintain the contrary : com- 
pare DESMOULiN’sj^iUfm. de la Soc. Med. ; Rathke, ap. ; Burdach, F/i^s. 
ii., p. 409 and 563 ; Herholdt, Oversigt, &c, 
t TiEDEMANiX, Juhelfeievy p. 25. 
