THE VOYAGE OF THE BEAGLE 



111 



seven degrees in mean temperature, but a greater one of 

 extreme heat, was sufficient to awake the functions of life. 

 At Monte Video, from which we had just before sailed, in 

 the twenty-three days included between the 26th of July 

 and the 19th of August, the mean temperature from 276 ob- 

 servations was 58°4; the mean hottest day being 65°.5, and 

 the coldest 46 0 . The lowest point to which the thermometer 

 fell was 4i°.5, and occasionally in the middle of the day it 

 rose to 69 0 or 70 0 . 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. 1 

 This shows how nicely the stimulus required to arouse hy- 

 bernating 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 hybernation, or more properly aestiva- 

 tion, of animals is determined not by the temperature, tut 

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

 surprised to observe, that, a few days after some little de- 

 pressions 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 acci- 

 dent 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 be- 

 lieve 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 ex- 

 tremity 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 hun- 

 dreds of these zoophytes might be seen, projecting like stub- 



