374 REPTILIA. 



the left being the lowest. When the ova are enlarged, fit to be laid, 

 they are nearly all of equal size. As they most probably lay them 

 nearly all at one time, not [consecutively at intervals] as birds and 

 insects do, and as it would appear that every part of which the ovaria 

 are composed has formed its egg, there being no smaller ones to come 

 on in another year, therefore most probably each nidus for the ovum 

 forms its ovum every year. I believe this is common to all of this tribe. 

 There are in each ovaria about twenty-four ova. There are two ovi- 

 ducts which are very convoluted, and begin almost by one opening like 

 a kind of funnel which divides into the two : this opening is between 

 the liver and the heart; each oviduct passes round the convex surface 

 of the liver to the loins 1 . 



[Order Ophidia.] 



Of Snakes. 



Snakes drink by suction, not by lapping as lizards do. 



The oesophagus in snakes is very thin ; therefore, as they are capable 

 of swallowing very large bodies, such as would appear to be beyond 

 the power of the gullet to push along, the power of deglutition must 

 be in the muscles of the trunk. 



The young snake as it forms upon the yolk, sinks into it and becomes 

 almost enclosed. The outer edge of the yolk would seem to rise round 

 the little animal, and then to be drawn in over it, only leaving a small 

 space covered by a transparent membrane, through which the snake is 

 seen with the head in the centre of the coil. They are often so coiled 

 up as to make a knot 2 . 



Of their Membranes. — At a pretty full-grown age there are two 

 membranes, one [allantois] enclosing the whole, which now lines every- 

 where the egg-shell [chorion], and which encloses the albumen, yolk, &c. 

 It is extremely tender, and appears more like the retina of the eye 

 than any other membrane I know. Its vessels, which are but small, 

 pass out from the [umbilical] cord through the other membrane. The 

 other membrane [vitellicle] is that which encloses the yolk, and which 

 I suspect is a double membrane now united, as in the chick, and pro- 

 bably formed in the same way ; for without its being a double mem- 

 brane it could not cover the space over the snake, through which it is 

 seen. These vessels of the membrane unite, and, within the inner 

 membrane they form the cord, which enters the abdomen of the animal. 

 There is a duct [vitelline duct] whose end begins at the yolk, having 

 its mouth open there : it passes along in the substance of the cord, and 



1 [Hunt, Preps. Phys. Series, Nos. 3327—3329.] * [ib. Nob. 3316, 3317.] 



