SOME RECENT MEMOIRS UPON OLIGOCHJETA. 193 



The original indigenous forms, South American in 

 character, may be regarded as having been gradually 

 driven to the west by the encroachment of artificially in- 

 troduced species. In other respects the geographical regions 

 indicated by the distribution of earthworms agree fairly well 

 with the generally received scheme of Mr. Sclater. The 

 Ethiopian region is peculiarly distinct ; the Neotropical is 

 also nearly if not quite as plainly marked ; but the Oriental 

 fades into the Australian, and it is indeed not easy to 

 separate them at all. 



The only other matter affecting the distribution of earth- 

 worms with which I shall deal here is the question of 

 oceanic islands. Our information upon the subject is not 

 however by any means extensive ; the largest collection 

 made is due to the energy of Mr. Perkins, and has been 

 described by me in a paper communicated to the Zoological 

 Society. These worms were gathered in the Sandwich Is- 

 lands, and belong to a number of species of which only two 

 (and a doubtful third) have not been found elsewhere ; 

 these two belong to the genus Perichccta, a genus prevalent 

 in tropical regions, especially of the old world. That the 

 bulk of the species known from these and other oceanic 

 islands are forms which have been in all probability intro- 

 duced by accidental transference by man is rather what might 

 be expected from the limited powers of independent travel 

 possessed by these animals. There is at present no certain 

 evidence that there are any truly indigenous earthworms in 

 oceanic islands, with the exception of Kerguelen — a fact 

 which as I have already hinted may be due to other causes. 



To Linnaeus only a single species of earthworm was 

 known, his Liimbricus terrestris, now believed to have beeii 

 a compound of more than one species. Grube in his 

 Familie der Anneliden, published in 1851, reckoned up 

 only forty-two earthworms, and of these one or two are 

 now known not to be earthworms at all, and of the re- 

 mainder many are unrecognisable or synonyms. Since that 

 period the increase of new forms has gone on — of late 

 with extreme rapidity ; at the present moment we are 

 acquainted with rather over 500 distinct and well char- 



