100 FROM FISH TO PHILOSOPHER 



of the skin to water and the active absorption of salt 

 are markedly increased by the removal of this inactive 

 epithehum. Contrariwise, salt and water absorption must 

 be considerably decreased in the arid-Hving toads, where 

 local thickening of the epidermis into warts foreshadows 

 the evolution of reptilian scales and plates, and the with- 

 drawal of the skin from active participation in salt and 

 water balance. 



No amphibian can Hve long in dry air: a frog or newt 

 exposed at room temperature and humidity will lose one- 

 quarter of its body weight in ten hours, a degree of desic- 

 cation that is lethal for most species. Legends of frogs 

 or newts recovered alive from the walls of buildings 

 where they have allegedly been buried for months or 

 years without water are the product of uncritical ob- 

 servation. No amphibian capable of estivation compara- 

 ble to that of the lungfishes is known; the nearest ap- 

 proach is among the desert-living frogs and toads that 

 hibernate during droughts in burrows a foot or so in the 

 earth. But even here the subterranean air is quite humid 

 and before hibernation the animal stores considerable 

 water in the urinary bladder, subcutaneous tissues, and 

 peritoneal cavity. Some of these hibernating frogs— 

 for instance Notaden bennetti, Heleioporus pictus, Cy- 

 clorana ( = Chiroleptes dboguttatus) of AustraHa— have 

 peritoneal funnels (coelomostomes) which drain into 

 venous sinuses in the kidney, and during hibernation wa- 

 ter stored in the peritoneal cavity is thus made available 

 to the circulation. It is certain that water may also be 

 reabsorbed from the urinary bladder for this purpose, if 

 the urine is relatively dilute. So rapidly can the dehy- 

 drated Australian frog absorb water through the skin, 

 a correspondent from Australia once reported to P. A. 

 Buxton, that *If you put a lean, dry, herring-gutted 

 Chiroleptes into a beaker with two inches of water, in 

 two minutes your frog resembles a somewhat knobby 

 tennis ball.' It is said that the water-loaded animals are 



