1833.] HIBERNATING ANIMALS. 71 



near the sea coast, and from its motvied colour, the brownish scales) 

 being speckled with white, yellowish-red, and dirty blue, can hardly 

 be distinguished from the surrounding 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 quickness in the loose sand. The 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, Sep- 

 tember 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 I5th, a few animals began to appear, and by the 

 1 8th (three days from the equinox), everything announced the com- 

 mencement of spring. The plains were ornamented by the flowers of 

 a pink wood-sorrel, wild peas, cenotherae, and geraniums ; and the birds 

 began to lay their eggs. Numerous Lamellicorn and Heteromerous 

 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 direction. 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 day 

 between sixty and seventy. Here then an increase of 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 ot 

 July and the igth of August, the mean temperature from 276 observa- 

 tions was 58 - 4; the mean hottest day being 65 0< 5, and the coldest 46. 

 The lowest point to which the thermometer fell was 4i'5, and occasion- 

 ally 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 seon that at Bahia Blanca, which is four degrees southward, 

 and therefore with a climate only a very little colder, this same tempera- 

 ture u-ith a rather less extreme heat, was sufficient to awake all orders of 

 animated beings. This shows how nicely the stimulus required to 

 arouse hybernating 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 aestivation, 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 hav^i 

 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 mu^d, He a4d,s, " The Indians often fiud 



