124 Proceedinc/s of the Royal Irish Academy. 



this paper, has for its nearest allies Helodrilus Molleri in Portugal, and 

 H. Mobii in Madeira, the Canaries, and Tangiers. 



According to the theory advanced by Michaelsen (22. p. 179) to explain 

 the present distribution of the Lumbricidae, the northern limit of the endemic 

 species coincides with the lower limit of the ice during the glacial epoch. 

 Species now found north of this line are supposed to have spread to their 

 present habitat since the retreat of the ice. The only part of the British 

 Isles which does not show glaciation is the south of England, and conse- 

 quently this is the only British locality where endemic species could occur. 

 This theory seems to explain admirably the Continental distribution of the 

 Lumbricidae. But it does not account for the presence in Ireland of those 

 species which are absent from Great Britain, and which have a characteristic 

 Mediterranean distribution. He dismisses them briefly by saying that they 

 are " stark peregrin," without telling us how they reached Ireland. Four 

 hypotheses may be advanced to explain their presence : — 



1st, that after being exterminated in Ireland by the ice, they spread from 

 the South of England to the West of Ireland, and flourished there, 

 whilst they became extinct in England ; 



2nd, that they reached Ireland by a continuous land-connection with the 

 South of France, or Portugal, since the Ice Age ; 



3rd, that they represent a Pre- Glacial fauna which survived the Ice Age ; 

 4th, that they were introduced by man. 



The first hypothesis, that they spread from England, may be dismissed as 

 improbable. The earthworm fauna of Ireland is richer than that of Great 

 Britain, and cannot have been altogether derived from it. There is, moreover, 

 no definite proof of a land-connection between Ireland and Great Britain 

 since the Ice Age. 



As to the second hypothesis, the evidence in favour of a Post-Glacial 

 land- connection with the South- West of Europe is very slight ; and, in any 

 case, it could hardly have lasted long enough to allow such slow-spreading 

 animals as earthworms to reach Ireland from the Mediterranean region. 



The theory of int.roduction by man has little to recommend it ; and 

 consideration of the present distribution shows that it is a quite inadequate 

 explanation. For instance, Lumhricus Friendi only occurs in the South of 

 Ireland in the British Isles, and has only been found elsewhere at consider- 

 able elevations in the Pyrenees and the Alps. It is somewhat difficult to 

 imagine this species being transferred by early visitors from such localities 



