GIANT LAND-TORTOISES 335 
survival in these islands of the reptiles under consideration 
is entirely due to the absence of such mammals. But, on 
the other hand, it has to be borne in mind that the giant 
Siwalik tortoise lived in a land where large mammals— 
both carnivorous and herbivorous—absolutely swarmed ; 
and the same was also the case with the other extinct 
continental species referred to above. Moreover, we have 
no evidence of the existence of large tortoises on the 
continents of the world at an epoch before the advent of 
large mammals. Still, the absence of the latter from 
practically all the tortoise-islands is a fact that cannot be 
disregarded, and must almost certainly have had a very 
great influence on the development of their chelonian 
inhabitants. 
In regard to the numbers in which giant tortoises 
formerly existed on the islands of the Indian Ocean, very 
few words must suffice. Writing in 1691, the French 
traveller Francois Leguat stated that in Rodriguez the 
tortoises covered the ground so thickly that in places you 
might walk a hundred paces or more by stepping from the 
back of one on to that of another. In Mauritius, though 
apparently less abundant, they were still very numerous 
down to 1740; and there is ample testimony that during 
the seventeenth and eighteenth centuries they also swarmed 
on Réunion, although not a single specimen of the species 
indigenous to that island has been preserved. The ease 
with which these reptiles could be captured and carried 
off, and the facility with which they could be kept alive on 
board, coupled with the large amount of excellent meat 
yielded by each, rendered them a valuable food-supply to 
the crews of ships, and it was far from uncommon for 
vessels leaving Mauritius to carry off a cargo of four 
hundred at a time, while in 1759 one of four vessels 
