THE VOYAGE OF THE BEAGLE 405 



doubted whether this frog is an aboriginal of these islands. 

 The absence of the frog family in the oceanic islands is the 

 more remarkable, when contrasted with the case of lizards, 

 which swarm on most of the smallest islands. May this dif- 

 ference not be caused, by the greater facility with which the 

 eggs of lizards, protected by calcareous shells, might be 

 transported through salt-water, than could the slimy spawn 

 of frogs? 



I will first describe the habits of the tortoise (Testudo 

 nigra, formerly called Indica), which has been so frequently 

 alluded to. These animals are found, I believe, on all the 

 islands of the archipelago; certainly on the greater number. 

 They frequent in preference the high damp parts, but they 

 likewise live in the lower and arid districts. I have already 

 shown, from the numbers which have been caught in a single 

 day, how very numerous they must be. Some grow to an 

 immense size: Mr. Lawson, an Englishman, and vice-gov- 

 ernor of the colony, told us that he had seen several so large, 

 that it required six or eight men to lift them from the 

 ground ; and that some had afforded as much as two hundred 

 pounds of meat. The old males are the largest, the females 

 rarely growing to so great a size: the male can readily be 

 distinguished from the female by the greater length of its 

 tail. The tortoises which live on those islands where there 

 is no water, or in the lower and arid parts of the others, feed 

 chiefly on the succulent cactus. Those which frequent the 

 higher and damp regions, eat the leaves of various trees, a 

 kind of berry (called guayavita) which is acid and austere, 

 and likewise a pale green filamentous lichen (Usnera plicata), 

 that hangs from the boughs of the trees. 



The tortoise is very fond of water, drinking large quan- 

 tities, and wallowing in the mud. The larger islands alone 

 possess springs, and these are always situated towards the 

 central parts, and at a considerable height. The tortoises, 

 therefore, which frequent the lower districts, when thirsty, 

 are obliged to travel from a long distance. Hence broad and 

 well-beaten paths branch off in every direction from the 

 wells down to the sea-coast; and the Spaniards by following 

 them up, first discovered the watering-places. When I landed 

 at Chatham Island, I could not imagine what animal travelled 



