56 COLLINGE : REVIEW OF THE ARIONIDrE OF THE BRITISH ISLES. 



July 15th. — "Have now probably assumed their final colour; 

 mantle, dull greyish-orange ; back grey ; light greyish-yellow at the 

 sides ; caudal region and gland yellower." 



On returning from a journey I notice on August 12th a cluster of 

 about a dozen eggs, strongly cemented together into an irregular 

 mass. They are globular, pearly white, and barely 2 mm. in 

 diameter. The slugs are now of a more uniform yellow or orange- 

 yellow, than when last described. 



From the above extracts from my note-book, it will be seen that 

 these slugs at different ages might have been described as distinct 

 varieties. I hope next year to observe the changes which take place 

 in those individuals which commence life with a yellow habit. 



A REVIEW OF THE ARIONID>£ OF THE 

 BRITISH ISLES. 



By WALTER E. COLLINGE, 



Assistant Demonstrator in Zoology, St. Andreios University. 



In attempting to review a family of Slugs such as the Arionidm, 

 I am only too conscious of how difficult a task I have undertaken 

 and of the ability and able memoirs of my predecessors, and yet 

 I venture to think that — imperfect as these pages must necessarily 

 be — the same will be of use and assistance to those who have not 

 had the facilities and advantages which I have been so generously 

 favoured with. 



Through the kindness of many conchologists I have had 

 unlimited supplies of material to work upon, and I take this 

 opportunity of thanking the many willing helpers who have so 

 generously assisted me, and to whom more special mention is made 

 hereafter. My thanks are specially due to the following gentlemen : — 

 Dr. R. F. Scharff, B.Sc, Keeper of the Natural History Museum, 

 Dublin, who has not only supplied me with specimens of all the 

 Irish Arionidtz, but throughout the preparation of these pages has 

 offered every assistance, and has most generously read over my MS. 

 before going to press ; to Prof. W. C. M'Intosh, M.D., LL.D., F.R.S., 

 who, during the latter part of July and the beginning of August, 

 allowed me to continue my researches, &c, at the St. Andrews' 

 Marine Zoological Laboratory ; to Mr. T. D. A. Cockerell, F.Z.S., 

 F.E.S., Curator of the Museum of the Institute of Jamaica, Kingston, 

 who has rendered most generous assistance and made many valuable 

 suggestions, as the following pages witness ; to Mr. E. W. Swanton, 



