The Classification and Distribution of Earthv^orms. 2G7 



increased to some extent, so that it seems worth while again to 

 collect the availahle data and to present them in a compact 

 form. The distribution of any group is worth studying as a 

 contribution to the general subject, but tlie Lumbricidfc are 

 of special interest, and for two principal reasons : — In the first 

 place they occur everywhere, and under nearly all conditions. 

 Accordingly, it is possible to test the influence which climate, 

 altitude, and other conditions exercise upon them. In the 

 second place, they are eminently land animals, and possess 

 but little power of dispersion through countries which are 

 separated by salt water. The animals themselves are in the 

 highest degree susceptible to salt water, and are killed by a 

 very short immersion. Darwin ^ particularly mentions this 

 fact in relation to their occurrence in Kerguelen and the 

 Falklands. 



But in spite of this fact, which seems to be probably of 

 general significance, there are, here and there, exceptions. 

 The most marked exception is the genus Pontodrilus. The 

 two species of this genus — P. littoralis^ and P. Marionis^ — 

 live habitually upon the sea-shore among the debris cast up 

 by the waves, but above the high- water mark. Both species 

 occur on the southern Trench coast near Marseilles, iSTice, 

 and Villefranche. 



This being the case, it is remarkable that earthworms have 

 not been made more use of in works dealing with geographical 

 distribution. Even so excellent a treatise as Professor 

 Heilprinn's recently published "Distribution of Animals" 

 contains no mention of the group. 



The barriers on land to the dispersal and migration of 

 earthworms are not many. They depend, so far as we know, 

 upon no special kind of soil, provided only it be sufficiently 

 damp. Eivers would hardly interfere, as so many (? all) 

 species withstand immersion in fresh water for a long period. 

 Deserts, however, would'; and it is to be noted that the 



^ The Formation of Vegetable Mould through Earthworms. London, 

 1880, p. 120. 



- Grube, E. , Ueber neue oiler wenig bekannten Anneliden— Arch. f. 

 Naturg., xli., p. 127. 



^ Pekrier, E., Etudes sur I'organisation des Lonibriciens, eto. — Arch. 

 Zool. Exp., t. ix. (1881), p. 176. 



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