278 



ME. It. TRIMEN'S NOTES ON THE GEOGRAPHICAL 



Darwin's masterly argument on this subject (Orig. of Spec, 

 chaps, xi. and xii.), but will merely observe that it meets Mr. 

 Murray's remarks, as if by anticipation, at every turn. 



In reference to the Atlantic Islands, and particularly to Ma- 

 deira, Mr. Murray (pp. 4 & 12) inquires with some emphasis 

 how it is that the endemic insular forms have not " found their 

 way to Europe" as easily as European species have found their 

 way to the islands, and states that "not a single example of 

 any of its [Madeira's] peculiar species " has ever so found its 

 way, " except in an entomologist's box." "Without inquiring too 

 closely how it was possible to ascertain the truth of the latter 

 statement, it should be observed that the question here is not so 

 much one of travelling as of establishment of an organism in a 

 country foreign to it ; and the answer to the question in this 

 view of it is really furnished by Mr. Murray himself (p. 62). 

 Following in Mr. Darwin's wake, he clearly shows how easily 

 and promptly unoccupied ground is seized upon by immigrants, 

 and how extremely difficult, on the contrary, it is for a foreign 

 form to effect an entrance, and still more to establish itself, on 

 land already well occupied. Oceanic islands are notoriously poorly 

 stocked, while Europe, for by far its greater portion, is rich in 

 nourishing forms ; so that, allowing the available means of trans- 

 port to and from Madeira to be equally great, it was scarcely 

 to be expected that Madeiran special forms should have the 

 same force to accomplish a permanent settlement on European 

 soil as continental species would possess to naturalize themselves 

 on the island. 



I regret that, on the two occasions on which I landed at 

 Ascension, my time was too limited to make any but the most 

 superficial exploration of a small portion of its area. I observed 

 no terrestrial animals of any sort, with the exception of thousands 

 of Musca domestica and its allies M. vomitoria and M. Ccesar, 

 and a few of Dermestes lardarius, all four such devoted followers 

 of mankind, that it is safe to regard them as introductions. I 

 was, however, informed by a resident that butterflies were occa- 



been formed, like other mountain-summits, of granite, metamorpkic schists, old 

 fossiliferous or other such rocks, instead of consisting of mere piles of vol- 

 canic matter." I notice a remark recently published ('Nature,' Dec. 22, 1870, 

 p. 148) by Dr. Hooker to the effect that the Seychelles group is formed of gra- 

 nite and quartz — a fact that widely distinguishes it from the Mascarene group 

 of volcanic formation. 



