GENUS LIMAX. 33 
InrERNALLY, Lima is especially characterized by the gut possessing five 
coils, in addition to the cesophageal or stomach tract, an arrangement dis- 
tinguished by the term Pentadroma'; its 
first and second courses are held in posi- 
tion by the cephalic aorta, as is usual im 
gastropods, the third and fourth tracis 
being retained anteriorly by encircling 
the pharyngeal retractor, the whole gut 
displaying no indication of the spiral 
twisting to which in the past it has been 
undoubtedly subjected. 
‘The RepRopUCTIVE ORGANS are simple, 
with few accessory parts, and according 
to Babor undergo in most species a cycle 
of development, the animal being first 
unisexual, and only subsequently herma- 
phrodite, but may finally again become 
unisexual by the atrophy of the organs 
of the sex to which the animal originally 
belonged ; the PENIS SHEATH is somewhat 
long, and the PENIS and VAGINA are 
separated by the right tentacular re- ,f0.S0: Dinas feu Lo,as conacted 
tractor ; SPERM DUCT a complete tube, arrangement of the internal organs. ‘ 
not incomplete as in Arion; circulatory (4: "scnecee ue call b heats eee 
system, according to Semper, shows a ~ intestine; 4. kidney ; liver. 
single oval blood sinus beneath; the SUPRA-PEDAL mucus gland is imbedded 
in the foot and extends the whole length of the body ; atrium short. 
The HEART and LUNG are constructed as in Helix and Hyalinia; the 
KIDNEY is a simple sac with laminate margins and furnished with a well- 
marked and distinct SECONDARY URETER.” 
Geographical Distribution.—Limax is naturally a western palie- 
aretic group, and in its dispersal strikingly evidences the truth of our 
location of the most active evolutionary area in North Central Europe, for 
we find the most highly organized forms prevailing there, fringed around 
with allied but more simply organized and weaker species, whose progenitors 
have probably been expelled therefrom or otherwise have taken refuge im 
more or less undesirable localities, as with the primitive Z. tenellus, which 
though still found in North Central Europe, is now almost exclusively re- 
stricted to the limits of the pine forests. 
The higher organization and greater adaptability of the dominant species 
of Limaa is shown by their quickly becoming accustomed to new surround- 
ings when accidentally transported to other countries, and gradually 
extending their range to the detriment and dispossession of the weaker 
aboriginal species. 
Geological History.—The genus Lima has been recorded as fossil 
from deposits as ancient as the Lower Miocene of Germany, and from other 
beds of more recent formation. 
In the British Isles this genus has been recorded by Morris from the 
Mammalian Crag at Stutton; it has also been found in the Lower Pleistocene 
of East Anglia, in the Middle Oligocene of the Hampshire Basin, and vari- 
ous other deposits. 
1 Monog. i., p. 285, f. 569, 2 Monog. i., p. 336, f. 628. 
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