GIANT TORTOISES AND THEIR DISTRIBUTION 315 



case. For it will be obvious that a female tortoise carrying 

 fertilised eggs within her body would suffice to secure the 

 propagation of her species on any land to which she might 

 have been carried, were such carriage possible. 



Nevertheless, the arguments of Dr. Baur appear conclusive 

 as to the continental, as distinct from the oceanic, origin of 

 the islands of the Galapagos group. That is to say, they 

 formerly constituted a portion of the South American con- 

 tinent, from which they were subsequently sundered and split 

 up by a great but gradual subsidence in the bed of the South 

 Pacific. That Polynesia is a subsiding area is now generally 

 admitted ; and, without entering on the difficult question as 

 to the existence of a land connection between South America 

 and Australia during comparatively late geological times by 

 way of Polynesia, it is quite probable that the severance of 

 the Galapagos from Equador formed one of the later episodes 

 of that subsidence. If I were asked to suggest an approximate 

 date for the severance, I should select as the most probable the 

 early part of the Miocene or the end of the Oligocene epoch. 



Turning to the giant tortoises of the islands of the Indian 

 Ocean, it may be premised that the arguments adduced by 

 Dr. Baur in favour of a continental origin for the Galapagos 

 will hold good also in this case. Madagascar, which, be it 

 noted, was formerly the home of giant tortoises, is admitted 

 on all sides to be a continental island, although opinions 

 differ with regard to the probable date of its separation from 

 the mainland. On the other hand, the Seychelles are regarded 

 by Dr. Wallace as having been isolated from Madagascar since a 

 very remote period, even if they were ever connected therewith, 

 although they may have had ample opportunities of receiving 

 from that island such immigrants as can cross narrow seas. 

 Mauritius and Reunion (Bourbon) are, however, considered to 

 be islands of antiquity which have never been connected with 

 Madagascar, and it is probable that Aldabra would be included 

 in the same category. 



A later observer. Dr. F. H. Standing, whose opinions are 

 based on the study of the subfossil, lemur-like mammals of 

 Madagascar, has arrived at conclusions differing essentially 

 from those of Dr. Wallace. He believes Madagascar to have 

 been connected with the African mainland till the Miocene ; 

 also that during the early portion of the Tertiary period 



