514 ScHARFF — On the Slugs of Ireland. 



the structure of the raduhi ; and new species have, in consequence, made their 

 appearance in overwhelming numbers. Simroth (38) changed this unfortunate 

 state of things by the production of an elaborate treatise on the German slugs, in 

 which he bases his classification chiefly on the form of tlie reproductive organs 

 and the intestine. He showed that the radula is subject to much individual 

 variation, and that it is, perhaps, the most unsuitable portion of the slug's body 

 for the purpose of classification. By his anatomical investigations he was enabled 

 to reduce considerably the number of European species, as given in such a recent 

 work as that of Westerlund (44). Among a number of species of Limax mentioned 

 in the latter work, fifteen supposed genuine species proved, on examination of the 

 internal organs, to be mere varieties of Limax maximtis. 



Slugs are not alone of importance as regards the geographical distribution of 

 animals. I hope to be able to show in a separate chapter that their colour has an 

 important bearing on the subject of colouring in animals generally. 



Thompson, in his Natural History of Ireland (43), mentions nine species of 

 slugs as occurring in this country. In tlie most recent list of Irish Mollusca 

 published in 1888, by Taylor and Eoebuck (42), this number has been increased 

 to ten, but one of these, as I shall endeavour to show later on, is only a variety. 

 I shall now add four species to the list of Irish slugs, one of which, however, has 

 already been recorded by Roebuck (35), in the Journal of Conchology. All these 

 thirteen species, with the exception of one, are also found in Grreat Britain. This 

 one species, viz. Geomalacus maculosus, is not only absent from Great Britain, 

 but also from France and Germany. It appears again in Northern Spain, in the 

 province of Asturias. In Ireland it has hitherto only been found in the County 

 Kerry. This part of Ireland has yielded so many peculiar animals and plants 

 that it deserves very much more attention than it has hitherto received. A 

 thorough scientific investigation of that interesting county would, no doubt, 

 reveal a number of forms new to the British fauna and flora. 



The thirteen species of Irish slugs belong to five genera, viz. Litnax, Agrio- 

 limax, Anialia, Avion, and Geomalacus. In most of the British text-books, the 

 three first are united under the genus Limax, but the reasons for separating them 

 will be found under the headings of the respective genera. Lessona and Pollonera 

 (21), and others, have placed the very common Irish slug Limax marginatus 

 (= arhorum) in a separate genus, Lehmannia, but I have not thought it advisable 

 to adopt this subdivision of the remaining species of Limax. 



The species of the three first genera can be very readily distinguished from 

 those of the genus Arion, by the absence of the caudal gland. This gland is 

 present in Geomalacus, but it is not nearly so conspicuous as in Arion, in which 

 its triangular opening at the end of the body is well seen. 



The colour of the mucus is not of very great importance, but it is rather 



