192 THE FOOD OF ANIMALS 



existed, upon islands of the Indian Ocean and East Pacific. 

 Regarding the food of those found in the Galapagos Islands, 

 Darwin (in A Nahvralisfs Voyage) speaks as follows: — "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, which is 

 acid and austere, and likewise a pale -green filamentous lichen, 

 that hangs in tresses from the boughs of the trees." 



Among the few Lizards which live upon plant food are the 

 true Iguanas and two interesting species from the Galapagos 

 Islands. The Common Iguana {Iguana tuberculata) of tropical 

 America is a large lizard of arboreal habit, which lives chiefly 

 upon leaves and fruit. The front teeth are simply conical, but 

 the crowns of the others are flattened from side to side, and have 

 saw-like edges. The upper and lower teeth work against one 

 another in such a way as to effectively masticate the food. A 

 West Indian ally of this form is depicted in fig. 433. 



The two plant-eating lizards of the Galapagos Islands are 

 both of large size, and all their teeth are laterally flattened, 

 while each is provided with three little projections from the 

 crown. Though simpler in nature than the serrated teeth of the 

 Iguanas, they work against one another in much the same way 

 and for a similar object. Of these two lizards one is the only 

 marine representative of its order and is appropriately called the 

 Sea-Lizard {Amblyrhynch^ls cristatus). It is able to remain for 

 a considerable time under water, and numbers of these lizards 

 browse in company upon submerged sea-weeds. The Galapagos 

 Land- Lizard [Conolopkus subcristatus) is a burrowing form, and 

 lives upon cactus-branches and the leaves of acacias and other 

 trees. 



AMPHIBIANS 



An example has already been given (p. 187) of birds which 

 when still in the nest are fed on animal food, becoming plant- 

 eaters when adult. Amphibians illustrate the converse of this, 

 for while the adults are invariably carnivorous, the larvae or 

 "tadpoles" (fig. 434) are herbivorous. The common Frog 

 [Ra7ia temporaria) will serve as an example, and in this creature 

 we find the jaws of the tadpole provided with firm horny beaks. 



