XVm INTRODUCTION. 



and Tate in 1866, no fiirtliei- additions were made to our slugs or any 

 notable contribution to their study for a period of nearly thirty-five years. 



The present or modern period of activity in the study of our slugs 

 began in 1882, when Mr. W. Denison Roebuck took up the subject as a 

 special line of research, and by the active co-operation of British concho- 

 logists received many thousands of slugs from all parts of the British Isles 

 for examination, forming an excellent groundwork for the true appreciation 

 of their distribution, variation, and developmental history. 



The late Air. Charles Ashford, the most skilful molluscan anatomist that 

 we have ever had in this country, soon became associated with Mr. Roebuck 

 in the good work, and made hundreds of dissections of the various species 

 and varieties, confirming the external specific characters of the various 

 species by demonstrating the differences in their internal structure. 



The impetus thus given to the study was the means of bringing other 

 investigators into the field, and greatly popularizing the subject. 



In Mr. Roebuck's paper on the British slug list, published simultane- 

 ously with the Conchological Society'.? list of British land and freshwater 

 mollusca, 1883, the specific status of 



17. Limax cinepeo-nigfer 

 was affirmed, and the name added to the British list. 



The close and .systematic examination of the anatomical and morpho- 

 logical character of the Arions soon showed that another species of Ariou : 



is. Apion subfuscus, 

 existed in this country, and although the first published notice of it as 

 British was by Herr D. F. Heynemann in 1885, yet the associated labours 

 of Mr. Ashford and Mr. Roebuck upon undoubted British specimens 

 independently established its claim to inclusion in the British H.st. 



Continued investigation of the ArionidiU resulted in the identification 

 in 1886 of Mabille's Arioii bourgu'ujnati, mainly by the aid of anatomical 

 evidence. The first mention of it as British was by Mr. John Emmet, 

 writing on behalf of Mr. Roebuck in the " Naturalist" for June 1886, and 

 later study disclosed that the supposed new discovery was but an autliori- 

 tative reinstatement of Dr. Johnston's Arion cirvum^cripfit-i. 



Another resurrection made by Mr. (leorge Roberts in 18S7 and Dr. R. F. 

 Scharfif in IS90 was Ariaii intenni'iliu!^. The real credit of the reinstate- 

 ment, however, was due to Dr. Scharif, who showed from anatomical 

 evidence that ^1. »;/«/;////« existed with us, although in 1887 Mr. Roberts 

 had given a clear description of its external morphology under the name of 

 Arhiii Jliioiin. iSnbseipient synonymic stndy demonstrated that these 

 names referred to one and the same .species, for which A. liitermedim was 

 the (iri"inal name. 



