354 DARWINISM chap. 



for being carried by mammalia or birds, and for floating in the 

 water, or through the air, while many are so small and so 

 light that there is jDractically no limit to the distances they 

 may be carried by gales and hurricanes. 



We may, therefore, feel quite certain that the means of dis- 

 tribution that have enabled the larger mammalia to reach the 

 most remote regions from a common starting-point, will be at 

 least as efficacious, and usually far more efficacious, with all other 

 land animals and plants ; and if in every case the existing 

 distribution of this class can be explained on the theory of 

 oceanic and continental permanence, with the limited changes 

 of sea and land already referred to, no valid objections can be 

 taken against this theory founded on anomalies of distribution 

 in other orders. Yet nothing is more common than for 

 students of this or that group to assert that the theory of 

 oceanic permanence is quite inconsistent A^th the distribution 

 of its various species and genera. Because a few Indian 

 genera and closely allied species of birds are found in Mada- 

 gascar, a land termed "Lemuria" has been supposed to have 

 united the two countries during a comparatively recent 

 geological epoch ; while the similarity of fossil plants and 

 reptiles, from the Permian and Miocene formations of India 

 and South Africa, has been adduced as further evidence of this 

 connection. But there are also genera of snakes, of insects, 

 and of plants, common to Madagascar and South America 

 only, which have been held to necessitate a direct land 

 connection between these countries. These views evidently 

 refute themselves, because any such land connections must 

 have led to a far greater similarity in the productions of 

 the several countries than actually exists, and would besides 

 render altogether inexplicable the absence of all the chief 

 types of African and Indian mammalia from Madagascar, and 

 its marvellous individuality in every department of the organic 

 world. ^ 



Powers of Dispersal as illustrated hy Insular Organisms. 



Having arrived at the conclusion that our existing oceans 

 have remained practically unaltered throughout the Tertiary and 

 Secondary periods of geology, and that the distribution of the 



1 For a full discussion of this question, see Island Life, pp. 390-420. 



