214 
ZOOLOGICAL GEOGRAPHY. 
[PART ITI. 
nected with Europe at a far remoter epoch, and ought therefore 
to exhibit to us a fauna composed almost entirely of peculiar 
forms both of birds and insects. Yet, so far from this being the 
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 this 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. Murray, 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 . — There is yet another group of Atlantic 
islands wdiich 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, show's 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 truly 
