GENUS ARION. 165 
The REPRODUCTIVE ORGANS are comparatively simple, and triaulic, 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 PENTS. is 
aborted, and the FLAGELLUM, DART-SAC, digitate VAGINAL GLANDS, and 
copulatory branch of the spermatheca are absent; the ovorssris is placed 
quite at the rear of the body, while the prostate or sPERM-pUCT is also not 
a closed tube, as in Limar, but is open laterally and communicates 
throughout its length with the oviduct. 
The SUPRA-PEDAL GLAND is not imbedded in the pedal musculature, but 
hes free upon the foot, and extends about half the total length of the body; 
but in addition to the dermal and locomotory mucosity, the Avions 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 Limacidew ; 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 Ar/ons have the same crepuscular and noc- 
turnal habits which so markedly characterize the Limucidw, hiding away 
beneath ee 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 beg exceptionally notice- 
able for the facility and readiness with whieh it makes use of this means 
of escape from a disagreeable or undesirable situation. ‘The slugs, and 
especially the Arvons, 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 Avions are very voracious, especially in early spring, when they eat 
ravenously, devouriyg 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. 
