The Earth ivorms of Ireland. ^ i 



numerous as the species. This, however, in tlic present state 

 of things cannot be avoided. 



The characters by which orroups nmy be formed are very 

 various. Habitat doubtless affects species very largely, and I 

 shall have to deal somewhat fully in another paper with this 

 topic. At the same time there is a certain amount of con- 

 stancy in the disposition of the setce, the position of the first 

 dorsal pore and the girdle, the arrangement of the papillce, the 

 colour, the presence or absence of turbid fluid, the shape of the 

 body and other external features, to merit attention. Rosa has 

 pointed out also that there is ground for improving our system 

 of classification by observing the w^ay in which the receptacula 

 seininis open from within outwards. In fact, so long ago as 

 1884, in his valuable little work on the Earthworms of Pied- 

 mont, he divided this genus, including Dcndrobcena, into four 

 groups, solely on the strength of this important character. 

 Since then our knowdedge has increased, and new worms have 

 been added to our lists, so that the analysis of the genus which 

 Rosa adopted only partially answers our purpose. So far as it 

 goes, however, it does not at all clash with that which I shall 

 follow in the present instance. 



So far as we are able at present to tabulate our indigenous 

 worms, the genus Allolobophora falls naturally into four well 

 marked groups. Two of these groups have hitherto been re- 

 presented in Great Britain by a solitary species in each 

 instance. A third has only one representative in England, 

 though two species belong to Ireland, while the fourth boasts 

 five British species. In the following arrangement I shall 

 simply extend that which I first submitted to the public in the 

 Essex Naturalist y^vXy, \'^<^2. 



Group I. Lumbricoidea. 



The worms of this group are large, and closely resemble Lumbricus, so 

 closely, in fact, as to have misled even Eisen himself, though he had 

 been the pioneer of systematic helmintholog}% They are usually dark 

 in colour, but may become lighter under the influence of their environ- 

 ment; the set£e are in four couples, the individuals of which are nearly 

 close together. The body is cylindrical in front and flattened behind, 

 showing that the worm is wont to lie exposed from its burrow just as 

 the Common Earthworm does. The first dorsal pore is usually well back, 

 while the male pores are on papillae. They exude a slimy mucus when 

 irritated, but no watery or turbid fluid, no coloured or pungent liquid. 

 Usually found in rich soil, either arable or pasture, and not averse to 

 manure; they reach their greatest dimensions in fat garden soil. 



