152 SPECIAL FEATURES 
and are no doubt due to the fact that the chances of 
the fish of one loch interbreeding with those of another 
are very small. There are also a considerable number 
of peculiar species or varieties of insects, but nothing 
comparable to the differences which separate the 
animals of the Galapagos Islands from those of the 
adjacent mainland. To add point to the contrast we 
may note that the area of the British Isles is in round 
numbers, 121,500 square miles, as contrasted with the 
3,000 square miles of the Galapagos Islands. Suchislands 
as the British Islands are called by Wallace continental, 
in contrast with the oceanic type. 
One more example of an island fauna may be given. 
In this case we shall take Madagascar, which is of the 
continental type, but is separated from the continent 
of Africa by a channel so deep and wide that it must 
be supposed that the connexion between the two was 
broken at an extremely remote period. The total area 
of this large island is nearly twice that of the British 
Isles, and there is much forest. The fauna is remark- 
ably rich, and is as markedly characterized by the 
animals it includes as by those of which it is devoid. 
Thus the island has no monkeys in its wide tropical 
forests, but has some thirty-three species of lemurs, 
which constitute half the mammalian population 
of the island. Insectivores are fairly numerous, and 
include in the tailless hedgehogs (Centetes) primitive 
forms whose nearest allies appear to be some shrews 
in the West Indian Islands. There are not many 
carnivores, and no true cats, but in addition to eight 
civets there is a relatively powerful animal called 
Cryptoprocta, about the size of a common cat, which 
belongs to the civet group. There are few rodents, and 
the enormous wealth of large ungulates, which is so 
