CHAP. XIX.] 



THE MADAGASCAR GROUP. 



397 



very deep sea — much deeper than that which divides Mada- 

 gascar from Africa, and we have therefore no reason to imagine 

 their former union. But they would nevertheless greatly facili- 

 tate the introduction of Indian birds into the Mascarene Islands 

 and Madagascar; and these facilities existing, such an immigra- 

 tion would be sure to take place, just as surely as American birds 

 have entered the Galapagos and Juan Fernandez, as European 

 birds now reach the Azores, and as Australian birds reach such 

 a distant island as New Zealand. This would take place the 

 more certainly because the Indian Ocean is a region of violent 

 periodical storms at the changes of the monsoons, and we have 

 seen in the case of the Azores and Bermuda how important a 

 factor this is in determining the transport of birds across the 

 ocean. 



Mr. Darwin's theory of the formation of atolls is now almost 

 universally accepted as the true one, and this theory implies 

 that the areas in question are still, or have very recently been, 

 subsiding. The final disappearance of these now sunken islands 

 does not, therefore, in all probability, date back to a very re- 

 mote epoch ; and this exactly accords with the fact that some 

 of the birds, as well as the fruit-bats of the genus Pteropus, are 

 very closely allied to Indian species, if not actually identical, 

 others being distinct species of the same genera. The fact that 

 not one closely-allied species or even genus of Indian or Malayan 

 mammals is found in Madagascar, sufficiently proves that it is 

 no land-connection that has brought about this small infusion of 

 Indian birds and bats ; while we have sufficiently shown, that, 

 when we go back to remote geological times no land-connection 

 in this direction was necessary to explain the phenomena of the 

 distribution of the Lemurs and Insectivora. A land-connection 

 with some continent was undoubtedly necessary, or there would 

 have been no mammalia at all in Madagascar ; and the nature 

 of its fauna on the whole, no less than the moderate depth of 

 the intervening strait and the comparative approximation of the 

 opposite shores, clearly indicate that the connection was with 

 Africa. 



Concluding remar'ks on " Lemuria!' — I have gone into this 

 question in some detail, because Dr. Hartlaub's criticism on my 



