SERPENTS. 115 



is nothing more than a receptacle for air, the reptile 

 having therefore always within it a supply of air that 

 will aerate the blood for a long time. 



Many years ago. when I had a school, my boys 

 were accustomed to make pets of snakes, and to carry 

 them about in their pockets. One of their amuse- 

 ments was, to take their pets to a deserted stone 

 quarry, which had become half-filled with water, and 

 give them a swim. They used to have races across 

 the quarry; and, as a rule, the snakes went straight 

 across. Sometimes, however, they would dive, flatten 

 themselves against the bottom of the quarry, and 

 there remain until they were roused by a stone dropped 

 over them. The time during which they would re- 

 main submerged was astonishing; and not even a 

 frog could hold out longer, if so long. 



Now, in the marine snakes, which spend almost 

 the whole of their time in the water, the lungs are 

 very large indeed ; so that the reptile can lie quietly 

 sleeping on the surface of the water, being kept afloat 

 by the large and inflated lungs. If the snake can be 

 detected in this position, it can be easily taken, as it 

 must partially empty the lungs before it can dive; 

 and this is a work of some little time, the reptile being 

 obliged to throw itself on its back. I imagine that 

 the specimen which was caught in Mr. Bennett's net, 

 must have been taken while it was thus lying asleep. 



Another point connected with respiration is, that 

 in the water snakes, the nostrils are furnished with a 

 structure which fulfils the same purpose as the corre- 

 sponding portion of the whales and dolphins. They 

 are fitted with a sort of valve, which effectually closes 



