CONSPICUOUS EFFECTS OF "WINDS. 295 



experience in maintaining themselves under the new conditions 

 of existence, their ultimate establishment there must generally 

 depend on t\vo individuals of the same species and of different 

 sexes being simultaneously, or almost simultaneously, carried to 

 the new country. On the other hand, the strength of regular 

 winds, such as monsoons, trade winds, ttc., would not seem to 

 be so great as that flying creatures, such as birds and insects, 

 could be carried away by them against their will, nor, indeed, 

 with such rapidity as would be requisite to enable them to 

 reach some distant destination before they had perished of 

 hunger. There are, however, a few cases in which such effects 

 of wind are apparently so obvious that they cannot be over- 

 looked or disput-d. 



The most conspicuous and often-discussed example is afforded 

 by the fauna of the islands lying near to, or at no great distance 

 from Africa, It has long been known that, as regards their ter- 

 restrial fauna, the Azores, Madeira, and the Canary Isles belong 

 to Europe, and that even their birds and insects are for the 

 most part only specifically distinct from those of Europe. Nay, 

 Dohrn has lately shown that even the Cape de Verde Islands, 

 which are divided from Africa only by narrow straits, belong, as 

 to the greater number of their animals, to the European region, 

 although a small admixture of species from the Ethiopian 

 region can be pointed out. Wollaston, Murray, and others 

 have attempted to explain this remarkable circumstance in the 

 following manner. They assume that all these islands were 

 formerly connected with Europe by the mythical Atlantis ; an 

 explanation which escapes all possibility of discussion and 

 merely appeals to the greater or less credulity of different in- 

 quirers. The explanation offered by Wallace in his latest work 

 is founded, on the contrary, on forces of which we can ac- 

 curately estimate the efficiency, and it seems to me that his 

 views are amply supported by their extreme probability. He 

 points out that in this region of the Atlantic, steady winds and 

 storms alike blow in the direction which would be required to 

 allow of such atmospheric currents having transported European 

 animals to these islands. As an indirect argument for the 

 correctness of this view he adduces the total absence of all land 



