176 bulletin: museum of comparative zoology. 



might readily populate unoccupied ground. Among certain genera it 

 is probable that such a method of distribution may, in sporadic 

 instances, obtain. That it is frequent and normal, however, is equally 

 improbable. It is well known that certain species of the temperate 

 zones retire from the higher latitudes of their summer range to winter 

 in more equable climes. In the course of such migrations they are 

 occasionally met with far from land. This seasonal migration for 

 example, is probably accountable for the occurrence of Lasionycferis 

 noctivagans among the Bermuda Islands. Large, strong-flying bats, 

 such as the Old World flying-foxes, often make nightly forays of great 

 length from their roosts to some favorite feeding-ground, and they may 

 even conceivably visit islands within sight of their mainland haunts; 

 but that oceanic islands are often populated in this way there is very 

 little evidence. Indeed, the very fact that where bats are found in 

 islands they have usually become more or less differentiated from 

 their nearest neighbors, and this in a uniform and constant manner, 

 is proof that such fortuitous methods of distribution as have been 

 claimed for these animals are largely inoperative. 



Dobson (in 1879) seems to have been the first to insist on the 

 erroneousness of this assumption as to the inutility of bats in zoogeo- 

 graphical study. For, he says, " even if it be granted that the Chirop- 

 tera possess great powers of dispersal, it is certain that quite nine- 

 tenths of the species avail themselves of them in a very limited degree 

 indeed, and it is significant that the distribution of the species is 

 limited by barriers similar to those which govern it in the case of 

 other species of mammals." He recalls also the possible transporta- 

 tion of bats from place to place by vessels. The West Indies are 

 beyond the winter range of the northern migratory bats; and, except 

 possibly in the case of a few species to be mentioned, it is almost 

 certain that the present chiropteran fauna of each island is quite 

 stationary. The presence of the less strongly-flying species on the 

 several islands may therefore confidently be assumed as evidence 

 either that they reached these islands by following some former land 

 bridge nearly or quite continuous, or that they are autochthonous. 



In the following discussion, the evidence of the terrestrial mammals 

 will be first considered. Of these, there are included in the present 

 list some thirty-seven species or subspecies. Eight of these may be 

 at once dismissed as introduced by human agency, viz.: Oryctolagus 

 cuniculus, Mus musculus, Epimys rattus, E. r. alexandrinus, E. norve- 

 gicus, Mungos birmanicus, Cercopithecus mona, C. sabaeus. Possibly 

 the deer occurring on Cuba should be added to this list. A compari- 



