214 ZOOLOGICAL GEOGRAPHY. [part hi. 



nected with Europe at a far remoter epoch, and ought therefore 

 to exhibit to us a fauaa composed almost entirely of peculiar 

 forms both of birds and insects. Yet, so far from this being tlie 

 case, the facts are exactly the reverse. Far more of the birds 

 and insects are identical with those of Europe than in the 

 other islands, and tlris difference is clearly traced to the more 

 tempestuous atmosphere, which is shown to be even now 

 annually bringing fresh immigrants (both birds and insects) to 

 its shores. We here see nature actually at work ; and if the 

 case of Madeira rendered her mode of action probable, that of 

 the Azores may be said to demonstrate it. 



Mr. "Wollaston has objected to this view that " storms and 

 hurricanes " are somewhat rare in the latitude of Madeira and 

 the Canaries; but this little affects the question, since the time 

 allowed for such operations is so ample. If but one very 

 violent storm happened in a century, and ten such storms 

 recurred before a single species of insect was introduced into 

 Madeira, that would be more than sufficient to people it, as we 

 now find it, with a varied fauna. But he also adds the import- 

 ant information that the ordinary winds blow almost uninter- 

 ruptedly from the north-east, so that there would be always a 

 chance of a little stronger wind than usual bringing insect, or 

 larva, or egg, attached to leaves or twigs. Neither Mr. Wollaston, 

 Mr. Crotch, Mr. A. Muri-ay, nor any other naturalist who 

 upholds the land-connection theory, has attempted to account 

 for the fact of the absence of so many extensive groups of 

 insects that ought to be present, as well as of all small 

 mammalia and reptiles. 



Cape Verd Islands. — Tliere is yet another group of Atlantic 

 islands which is very little known, and which is usually con- 

 sidered to be altogether African — the Cape Verd Islands, situated 

 between 300 and 400 miles west of Senegal, and a little to the 

 south of the termination of the Sahara. The evidence that we 

 possess as to the productions of these islands, shows that, like 

 the preceding groups, they are truly oceanic, and have probably 

 derived their fauna from the desert and the Canaries to the 

 north-east of them rather than from the fertile and more trulv 



