GENUS LIMAX. 



33 



Fig. 50. — Lima.x JlaTus L., as contracted 

 afttr scalding, laid open dorsally to show the 

 arrangement of the internal organs. 



5/. crop or ftiTtctional stomach ; fn>. oviduct 

 ot. ovotestis ; sit. shell; A. heart; r. rectum 

 ;'. intestine ; /.-. kidney ; /. li\er. 



Internally, Lima.v is especially characterized by the gut possessing five 

 coils, in addition to the a3Sopliageal or stomacli 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 iu 

 gastropods, the third and fourth tracts 

 being retained anteriorly by encircling 

 the pharyngeal retractor, the whole gut 

 displaying no indication of the spiral 

 twisting to which in tlie past it has been 

 undoubtedly subjected. 



The Reproductive 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- 

 tractor; sperm duct a complete tube, 

 not incomplete as in Arion ; circulatory 

 system, according to Semper, shows a 

 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 Jlydluwi ; the 

 kidney is a simple sac with laminate margins and furnished with a well- 

 marked and distinct secondary ureter.- 



Geographical Distribution. — Llnvix is naturally a western palre- 

 arctic 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, wdiose progenitors 

 have probably been expelled therefrom or otherwise have taken refuge in 

 more or less undesirable localities, as with the primitive L. tenellus, which 

 though still found in North Central Eurojie, is now almost exclusively re- 

 stricted to the limits of the pine forests. 



The higher organization and greater adaptability of the dominant species 

 of Linidx 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.r 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 Stiitton : it has also been f )uud in the Lower Pleistocene 

 of East Anglia, in tlie Middle Oligocene uf the Hampsliire Basin, and vari- 

 ous other deposits. 



1 Monog. 1., p. 28.1, f. .5(!;i. 2 .Monog. i., p. 33B, f. C2S. 

 25/8/02 " C 



