230 ARlON CIRCUMSCRIP'fU'S. 



Reproduction and Development— The congress of this species has 

 been observed by iMr. E. J. Lowe, who remarks that the act is, as in Arion 

 //oi-fi'iisis, very transient, scarcely occupying more than forty to forty-five 

 seconds, but the spermatophore has not as yet been noticed or described. 

 Tiie eggs are deposited in moist sheltered positions, in clusters of twelve 

 to fifteen, adherent hy a sticky mucus, and have been observed from 

 June up to November; they are oval, but somewhat variable bothin shape 

 and size, usually of a seniitransparent white when first deposited, but 

 gradually becoming opalescent ov pearly. The young are said to be usu- 

 ally of a delicate grey, and to sliow the lateral banding from birth, as well 

 as a distinct dorsal keel, the latter, however, is usually gradually lost 

 during growth, its position being represented by a line of whitish mid- 

 dorsal tubercles at maturity, a state which would seem to be attained 

 about June and July. 



Food and Habits. — This species is much less slimy than Arion 

 hortenis, and unlike that species, is essentially a frequenter of grass fields 

 or uncultivated ground, and not common in gardens. Like its ally, it 

 however is a truly geophilous and nocturnal species, and in feeding only 

 ascends a short distance up a plant, though capable of spinning mucous 

 threads both in its young and adult state. 



According to Baudon, it is rather common on decaying tree-trunks, 

 under fallen leaves, and in the stem and cap of large mushrooms of which 

 and other fungi .1. circumscriptus is particularly fond. 



It is a very sluggish and slow species, bunching up and spreading out its 

 margins when at rest, and remaining inert as though torpid. It fixes itself to 

 wood or stone, and according to Mr. Sherriff Tye, when humped-up in such 

 places, looks like a grey pebble, and does not seek to escape from the place 

 where it is fixed. According to Baudon, it often excavates little galleries in 

 the earth under old trunks, in which many individuals may congregate, and 

 which serve for retreats when the temperature is too hot or too cold. 



Mabille describes it as a winter species in France, but in this country 

 the winters are more severe and it is rarely met with at that season. 



In captivity, Dr. Scharff found them to eat pieces of apple or rhubarb 

 stalk, while in the garden they seemed to prefer to feed' on the fallen and 

 partially-decayed flowers of the pea, instead of attacking the living parts 

 of the plant, like A. agresth. Mr. Gain found this species to thrive and 

 breed freely in confinement, but of 193 different kinds of food offered, only 

 thirty-three were taken freely, while ninety were totally rejected. 



Variation. — This species, being one of our more primitive and ancient 

 forms, does not display that wealth of variation shown by the more 

 recently evolved species, and although many varieties and even species 

 have been set up, based chieHy upon the difi'ering shades of dermal colour- 

 ing, yet these are all clearly referable to two chief lines of variation ; one, 

 which is chiefly found on cultivated land and gardens, is distinguished by 

 the yellowish or brownish shade of its colouring, due to the development 

 during growth of a number of reddish tegumentary pigment cells ; the 

 other partakes of the grey tint of the typical form, but is liable to darken 

 with age, and also displays more distinctly a certain concentration of the 

 yellow ])igment in the form of a supra-pedal longitudinal zone, and is a 

 form more especially rliaract(<ris(ic of the open country. 



The slight dorsal keel, invariably present in the immature individuals, 

 but whicli is usually gradually obliterated during growtli, may, however, 



