VOL. LVI.3 PHILOSOPHICAL TRANSACTIONS. 327 



maceration by remaining too long in the water; whereas the foetus in utero suf- 

 fers no injury from continuing its full number of months in the fluid he swims in: 

 the reason is, that water is a powerful solvent, and penetrates the pores of the 

 skins of land animals, and in time can dissolve them ; whereas the liquor amnii 

 is an insipid soft fluid, impregnated with particles more or less mucilaginous, and 

 utterly incapable of making the least alteration in the cutis of the foetus. 



Otters, beavers, and some kinds of rats, go occasionally into the water for 

 their prey, but cannot remain very long under water. Dr. P. has often gone to 

 shoot otters, and watched all their motions; he has seen one of them go softly 

 from a bank into the river, and dive down, and in about 1 minutes rise, at 10 

 or 15 yards from the place he went in, with a middling salmon in his mouth, 

 which he brought on shore; Dr. P. shot him, and saved the fish whole. Now, 

 as all fcEtuses have these passages open, if a whelp of a true water spaniel was 

 immediately after its birth served as the phoca does her cubs, immersed in water, 

 to stop respiration for a little time every day, Dr. P. makes no doubt but the hole 

 and canal would be kept open, and the dog be made capable of remaining as long 

 under water as the phoca. 



Frogs, how capable soever of remaining in the water, yet cannot avoid living 

 on land, for they respire; and if a frog be thrown into a river, he makes to the 

 shore as fast as he can. The lizard kind, such as may be called water lizards, or 

 lacertae aquaticae, are all obliged to come to land and deposit their eggs, to rest, 

 and sleep; even the crocodiles, who dwell much in rivers, sleep and lay their eggs 

 on shore; and, while in the water, are compelled to rise to the surface to breathe; 

 yet, from the texture of his scaley covering, he is capable of remaining in the 

 water longer by far than any species of the phocae, whose skin is analogous to 

 that of a horse or cow. 



The hippopotamus, who wades into the lakes or rivers, is a quadruped, and 

 remains under the water a considerable time ; yet his chief residence is on land, 

 and he must come on shore for respiration. The testudo, or sea tortoise, though 

 he goes out to sea, and is often found far from land; yet, being a respiring ani- 

 mal, cannot remain long under water. He has indeed a power of rendering him- 

 self specifically heavier or lighter than the water, and therefore can let himself 

 down to avoid an enemy or a storm ; yet he is under a necessity of rising fre- 

 quently to breathe, for reasons given before: and his most usual situation, while 

 at sea, is on the surface of the water, feeding on the various substances that 

 float in great abundance every where about him ; these animals sleep securely on 

 the surface, but not under water, and can remain longer at sea than any others 

 of this class, except the crocodile, because, as it is with the latter, his covering 

 is not in danger of being too much macerated; yet they must go on shore to 

 copulate and lay their eggs. 



