COLLINGE : REVIEW OF THE ARIONID^ OF THE BRITISH ISLES. 65 



Variation. — Mr. W. A. Gain very kindly sent me the following 

 descriptions. None of the variations seem to be important enough 

 to name (excepting, perhaps, No. i), and are probably due in a 

 large measure to the slime and food. 



Form 1 (var. nov. plumbeus, Cllge). Body very dark grey; 

 mantle and tail only slightly tinged with orange ; sole very slightly 

 coloured, pale cream with darker central portion. Habitat, Newark. 

 Dr. Scharff records this variety from Lough Caragh, in Kerry, and 

 from Connemara, West Ireland. 



Form 2. Body pale grey, almost white, faintly tinged with 

 yellow ; mantle pale yellow lines, extremely faint ; sole as type. 



Form 3. A green form from Ossington. Were young specimens 

 which lost this peculiar green tinge as they grew older. 



Form 4. Very pale yellow, almost white, colour nearly uniform, 

 excepting mucous gland and the sole, which are rather deeper in 

 colour. No lines on the sides or around the mantle. 



Arion hortensis, Fer., 1819. 



Body dark grey, light brown or blue ; lateral bands generally 



much darker than the ground colour, continued to front of 



mantle ; head and tentacles dark greyish-blue ; sole red or 



yellowish, sometimes white; foot-fringe variable; ruga? oblong, 



closely set, coarse. Slight indications of a keel in young 



specimens. Shell calcareous granules cemented together in 



a somewhat oval mass. 



This is, perhaps, the most perplexing of any of our British Arions, 



assuming almost every colour variation conceivable. Pollonera has 



made a number of species out of the various forms. 



Anatomy. — Both upper and lower vestibules are present, the 

 latter being the larger. The oviduct is long, and larger in the lower 

 portion. The large retractor muscle supplies both receptaculum 

 seminis and oviduct. There is seldom any marked difference between 

 the upper and lower portion of the vas deferens. Scharff gives a very 

 typical drawing of the reproductive organs of this species (pi. lvii, 

 fig. 34). A figure of Pollonera's (30 pi. ix., fig. 22) is, I fancy, 

 a variation. 



Reproduction. — The eggs are deposited from June to October, 

 and are generally in clusters varying from 30 to 40. They are 

 perfectly round and have a diameter of 2 mm. 



Variation. — Numerous species and varieties have been made 

 from immature examples of this species. A. hortensis differs very 

 markedly when young from the adult form, so much so that great 

 care should be exercised before assigning to this or that species. 



