CHAP. XIX THE MADAGASCAR GROUP 447 



Aldabra; in the Seychelles we have the fragments of 

 another very ancient island, which may perhaps never 

 have been continental; in Mauritius, Bourbon, and 

 Eodriguez we have three undoubtedly oceanic islands; 

 while in the extensive banks and coral reefs of Cargados, 

 Saya de Malha, the Chagos, and the Maldive Isles, we 

 have indications of the submergence of many large islands 

 which may have aided in the transmission of organisms 

 from the Indian Peninsula. But between and around all 

 these islands we have depths of 2,500 fathoms and 

 upwards, which renders it very improbable that there has 

 ever been here a continuous land surface, at all events 

 during the Tertiary or Secondary periods of geology. 



It is most interesting and satisfactory to find that this 

 conclusion, arrived at solely by a study of the form of the 

 sea-bottom and the general principle of oceanic per- 

 manence, is fully supported by the evidence of the organic 

 productions of the several islands ; because it gives us 

 confidence in those principles, and helps to supply us with 

 a practical demonstration of them. We find that the 

 entire group contains just that amount of Indian forms 

 which could well have passed from island to island ; that 

 many of these forms are slightly modified species, in- 

 dicating that the migration occurred during late Tertiary 

 times, while others are distinct genera,, indicating a more 

 ancient connection ; but in no one case do we find animals 

 which necessitate an actual land-connection, while the 

 numerous Indian types of mammalia, reptiles, birds, and 

 insects, which must certainly have passed over had there 

 been such an actual land-connection, are totally wanting. 

 The one fact which has been supposed to require such a 

 connection — the distribution of the lemurs— can be far 

 more naturally explained by a general dispersion of the 

 group from Europe, where we know it existed in Eocene 

 times ; and such an explanation applies equally to the 

 affinity of the Insectivora of Madagascar and Cuba ; the 

 snakes (Herpetodryas, &c.) of Madagascar and America ; 

 and the lizards (Cryptoblepharus) of Mauritius and 

 Australia. To suppose, in all these cases, and in many 

 others, a direct land-connection, is really absurd, because 



