98 ANIMAL LIFE IN DESERTS 



pools are unsuited to it, and it is only found in places 

 in which it will be exposed to desiccation periodically. 

 This animal can contain so much fluid that it is 

 occasionally used by the Australian aborigine as a 

 source of drinking-water. It appears to imbibe the J 

 water through its skin, as weU as its mouth, and to 

 do so very rapidly ; an AustraUan friend, Mr. L. 

 Harrison, writes to me that if you " put a lean, dry, 

 herring-gutted Chiroleptes into a beaker with 2 inches 

 of water, in two minutes your frog resembles a 

 somewhat knobly tennis-ball." 



iii. Heat and Relative Humidity 



These two factors must be considered together 

 because under natural conditions a high temperature 

 and a low relative humidity are generally associated 

 (page 23). It is not therefore possible, in the 

 absence of experimental work, to discriminate 

 between the effects of the two. 



The very existence of small animals on the surface 

 of the desert at midday is remarkable. Most of 

 these animals — for example, the Hzards and beetles 

 — are cold-blooded, so that one supposes that their 

 temperatures approximate to that of the air in 

 which they find themselves at any given time ; 

 and as they are relatively small the fluctuations of 

 their internal temperatures must be rapid. In 

 spite of this, animals do manage to exist on the 

 desert soil even in the middle of the day in summer. 



Good examples among the reptiles are the Agama 

 lizard at Ur of the Chaldees, to which reference has 

 been made (page 92), and the Chuckwalla (Sauro- 



