98 BAHIA BLANCA. [chap. v. 



surface. When frightened, it attempts to avoid discovery by 

 feigning death, with outstretched legs, depressed body, and 

 closed eyes : if further molested, it buries itself with great quick- 

 ness in the loose sand. This lizard, from its flattened body and 

 short legs, cannot run quickly. 



I will here add a few remarks on the hybernation of animals 

 in this part of South America. When we first arrived at Bahia 

 Blanca, September 7th, 1832, we thought nature had granted 

 scarcely a living creature to this sandy and dry country. By 

 digging, however, in the ground, several insects, large spiders, 

 and lizards were found in a half torpid state. On the 15th, a 

 few animals began to appear, and by the 18th (three days from 

 the equinox), every thing announced the commencement of 

 spring. The plains were ornamented by the flowers of a pink 

 wood-sorrel, wild peas, Oenotheras, and geraniums ; and the birds 

 began to lay their eggs. Numerous Lamellicorn and Hetero- 

 merous insects, the latter remarkable for their deeply sculptured 

 bodies, were slowly crawling about ; while the lizard tribe, the 

 constant inhabitants of a sandy soil, darted about in every direc- 

 tion. During the first eleven days, whilst nature was dormant, 

 the mean temperature taken from observations made every two 

 hours on board the Beagle, was 51; and in the middle of the 

 day the thermometer seldom ranged above 55. On the eleven 

 succeeding days, in which all living things became so animated, 

 the mean was 58, and the range in the middle of the clay between 

 sixty and seventy. Here then an increase of seven degrees in 

 mean temperature, but a greater one of extreme heat, was suffi- 

 cient 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 observations was 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 ex- 



