CHAP. XXII. CONSIDERED WITH REFERENCE TO TRANSMUTATION. 445 



scarcest, and others formerly scarce are now most numerously 

 represented. The variety-making force has been at work 

 with such energy — perhaps we ought to say, has had so much 

 time for its development — that almost every isolated rock 

 within gun-shot of the shores has its peculiar living forms, or 

 those very marked races to which Mr. Lowe, in his excellent 

 description of the fauna, has given the name of " sub-species." 



Since the fossil shells were imhedded in sand near the 

 coast, these volcanic islands have undergone considerable 

 alterations in size and shaj)e by the wasting action of the 

 Waves of' the Atlantic beating incessantly against the cliffs, so 

 that the evidence of a vast lapse of time is derivable from 

 inorganic as well as from organic phenomena. 



During this period no mammalia, not even of small species, 

 excepting bats, have made their appearance, whether in 

 Madeira and Porto Santo or in the larger and more numei'ous 

 islands of the Canarian group. It might have been expected, 

 from some expressions met with here and there in the " Origin 

 of Species," though not perhaps from a fair interpretation of 

 the whole tenor of the author's reasoning, that this dearth of 

 the highest class of vertebrata is inconsistent with the powers 

 of mammalia to accommodate their habits and structures to 

 new conditions. Why did not some of the bats, for example, 

 after they had greatly multiplied, and were hard pressed by 

 a scarcity of insects on the wing, betake themselves to the 

 ground in search of prey, and, gradually losing their wings, 

 become transformed into non-volant insectivora ? Mr. Darwin 

 tells me that he has learnt that there is a bat in India which 

 has been known occasionally to devour frogs. One might also 

 be tempted to ask, how it has happened that the seals which 

 swarmed on the shores of Madeira and the Canaries, before the 

 European colonists arrived there, were never induced, when 

 food was scarce in the sea, to venture inland from the shores, 

 and begin in Teneriffe, and the Grand Canary especially, and 



