GENUS ARION. 165 



The REPRODUCTIVE ORGANS are comparatively simple, and triaulio, the 

 EPIPHALLUS, OVIDUCT, and SPERMATHECA all Opening into what has been 

 termed the upper vestibule or egg-sac, which is formed by an expansion 

 of the free-oviduct, and according to Dr. Babor, becomes most marked 

 when the animal is in the male phase of its development ; the penis is 

 aborted, and the flagellum, dart-sac, digitate vaginal glands, and 

 copulatory branch of the spermatheca are absent ; the ovotestis is placed 

 quite at the rear of the body, while the prostate or sperm-duct is also not 

 a closed tube, as in Limax, but is open laterally and communicates 

 throughout its length with the oviduct. 



The supra-pedal gland is not imbedded in the pedal musculature, but 

 lies free upon the foot, and extends about half the total length of the body ; 

 but in addition to the dermal and locomotory muoosity, the Af-ions produce 

 a very gelatinous mucus with great rapidity at the caudal sinus, which at 

 pairing time becomes very abundant, and which is slowly devoured by the 

 prospective partner during the preliminary circular promenade. 



Reproduction and Development. — The congress of the species of 

 this genus is preceded by the prolonged circular procession and many of 

 the amatory dallyings described under the Lhnacidw ; the normal intro- 

 mittent organ has, however, become aborted, and the union is now effected 

 by the eversion of the oviduct, powerful retractor muscles being developed 

 for the withdrawal of the organ into the body when the union has been 

 consummated, the seminal element being transferred by means of an 

 elongate and multidenticulate spermatophore, which, though quite pliable 

 when fresh, becomes hardened by exposure to the air ; it, however, 

 speedily disintegrates or dissolves when lodged in the spermatheca. 



The duration of life is probably usually about one year, but in the west 

 of Ireland and other mild localities this period may be prolonged to even 

 double that time. This restriction of the age attained is perhaps in part 

 explainable by the absence of an external shell, which would materially aid 

 them to endure hot, cold, and more especially dry seasons. 



Food and Habits. — The Arions have the same crepuscular and noc- 

 turnal habits which so markedly characterize the Limacidw, hiding away 

 beneath rubbish, stones, logs, etc., or burrowing into the earth for conceal- 

 ment during the day, and only appearing at sunset to enter upon their 

 foraging expeditions, except during very cloudy or showery weather, when 

 they may be frequently seen crawling about during the day. 



They are very slow and sluggish in their movements, but when young 

 are adepts in slime-spinning, Arion subfuscus being exceptionally notice- 

 able for the facility and readiness with which it makes use of this means 

 of escape from a disagreeable or undesirable situation. The slugs, and 

 especially the Arions, do not, however, seem to possess the same recupera- 

 tive power as the testaceous species, a comparatively slight injury nearly 

 always proving fatal in its effects. 



The Arions are very voracious, especially in early spring, when they eat 

 ravenously, devouring almost any animal or vegetable substances, fresh or 

 decaying, that they meet with ; they are not only carnivorous and canni- 

 balistic but often coprophagous. 



Fossil. — A species attributed to Arion, the indifferens of Boettger, has 

 been found in the Lower Miocene of Niederrad, near Frankfort-am-Main, 

 but no traces of the genus have been met with in this country lower than 

 the Pleistocene beds. 



