IS33-] HIBERNATING ANIMALS. 107 



58.4° ; the mean hottest day being 65.5°, and the coldest 46°. 

 The lowest point to which the thermometer fell was 41.5°, 

 and occasionally in the middle of the day it rose to 69° or 70°. 

 Yet with this high temperature, almost every beetle, several 

 genera of spiders, snails, and land-shells, toads and lizards 

 were all lying torpid beneath stones. But we have seen 

 that at Bahia Blanca, which is four degrees southward, 

 and therefore with a climate only a very little colder, this 

 same temperature with a rather less extreme heat, was 

 sufficient to awake all orders of animated beings. This 

 shows how nicely the stimulus required to arouse hibernat- 

 ing animals is governed by the usual climate of the district, 

 and not by the absolute heat. It is well known that within 

 the tropics, the hibernation, or more properly sestivation, of 

 animals is determined not by the temperature, but by the 

 times of drought. Near Rio de Janeiro, I was at first 

 surprised to observe that, a few days after some little 

 depressions had been filled with water, they were peopled 

 by numerous full-grown shells and beetles, which must 

 have been lying dormant. Humboldt has related the strange 

 accident of a hovel having been erected over a spot where a 

 young crocodile lay buried in the hardened mud. He adds, 

 "The Indians often find enormous boas, which they call 

 uji, or water-serpents, in the same lethargic state. To 

 reanimate them they must be irritated or wetted with 

 water. " 



I will only mention one other animal, a zoophyte (I 

 believe Virgularia Patagonica\ a kind of sea-pen. It 

 consists of a thin, straight, fleshy stem, with alternate rows 

 of polypi on each side, and surrounding an elastic stony 

 axis, varying in length from eight inches to two feet. The 

 stem at one extremity is truncate, but at the other is 

 terminated by a vermiform fleshy appendage. The stony 

 axis which gives strength to the stem may be traced at this 

 extremity into a mere vessel filled with granular matter. 

 At low water hundreds of these zoophytes might be seen, 

 projecting like stubble, with the truncate end upwards, a 

 few inches above the surface of the muddy sand. When 

 touched or pulled they suddenly drew themselves in with 

 force, so as nearly or quite to disappear. By this action, 

 liie highly elastic axis must be bent at the lower extremity, 

 where it is naturally slightly curved ; and I imagine it is by 

 this elasticity alone that the zoopliyte is enabled to rise 

 again through the mud. Each polypus, though closely 



