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 practically 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 with 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. 1 
Powers of Dispersal as illustrated by 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 tliis question, see Island Life, pp. 390-420. 
