SQUAMATA 143 



shore swimming about. When in the water this lizard swims with perfect 

 ease and quickness, by a serpentine movement of the body and flattened tail — 

 the legs being motionless and closely collapsed to the sides. A seaman on board 

 sank one, with a heavy weight attached to it, thinking thus to kill it directly; 

 but when an hour afterward he drew up the line it was quite active. Their 

 limbs and strong claws are admirably adapted for crawling over the rugged 

 and fissured masses of lava, which everywhere forms the coast. The nature 

 of this lizard's food (seaweed) as well as the structure of the tail and feet, and 

 the fact of its having been seen voluntarily swimming out at sea, absolutely 

 proves its aquatic habits; yet there is in this respect one strange anomaly, 

 namely, that when frightened it will not leave the island. Hence it is easy 

 to drive these lizards down to any little point overhanging the sea, where 

 they will sooner allow a person to catch hold of their tails than jump into the 

 water. They do not seem to have any notion of biting; but when much 

 frightened they squirt a drop of fluid from each nostril. I threw one several 

 times as far as I could into a deep pool left by the retreating tide, but it invari- 

 ably returned by a direct line to the spot where I stood. It swam near the 

 bottom, with a very graceful and rapid movement, and occasionally aided 

 itself over the uneven ground with its feet. As soon as it arrived near the edge, 

 but still being under water, it tried to conceal itself under the tufts of seaweed, 

 or it entered some crevice. I several times caught the same lizard by driving 

 it to a point, and, though possessed of such perfect powers of diving and 

 swimming, nothing could induce it to enter the water; and as often as I threw 

 it in it returned in the manner described above. Perhaps this singular piece 

 of apparent stupidity may be accounted for by the circumstance that this 

 reptile has no enemies whatever on shore, whereas at sea it must often fall a 

 prey to the numerous sharks. 



These lizards are of much interest as indicating one of the ways 

 in which true land reptiles have become aquatic in their habits. 

 Tempted by the abundance of food growing in shallow water a 

 little beyond their reach, the reptiles ventured farther and farther 

 to obtain it. The tail gradually became a propelling organ, 

 though the lizard still retained in large measure its land habits 

 and land feet, because of the dangers from its water enemies. It 

 is not at all improbable that, in course of time, were these Galapagos 

 lizards left unmolested, they would become fleeter swimmers by 

 the development of a terminal caudal fin and paddle-like legs, 

 thus competing with their aquatic enemies and no longer needing 

 recourse to the land for protection. They also serve to indicate 

 that long tailed aquatic reptiles never used their legs to an appre- 

 ciable extent as organs of propulsion in the water. 



