24G 
ALlMKM’i’AUY SYSTEM- -HIND-GUT OK INTESTINE. 
closely siiiTOunded by or imbedded M itbiii the large and miiltilobed 
liver or digestive gland, which yields a digestive ferment. Sometimes 
there are several noticeable dilatations in this region, the most 
anterior of which may function as a crop and others as grinding- 
gizzards for the more etfective trituration of the food before arriving 
at the true stomach or digestive sac. 
The Terminal and post-median part or hind-gnt comprises the 
intestinal tract beyond the stomach, which, though much longer 
than the body containing it, is not, as might be rashly supposed by 
the uninitiated, indiscriminately coiled within the cavity without 
any particular or definite arrangement of its often long and numerous 
tracts, for each species, and more especially those of ])hyto})hagou,s 
or omnivorous habit, e.xhibits the most intricate, yet marvellously 
regular convolutions, the peculiarities of which are so markedly 
special to each species that many forms can be identified by this 
Fi(j. li)7- Fig. 498. 
Fig. 197. - Alimentary tract of Arion hortensis F(fr., X 1, Horsforth, near Leeds, showing the 
conjj)le.\ intestinal convolutions of an omnivorous species. 
Fig. 198. — .\liinenlary tract of Tvstacclla lialiotidea Drap,, X 2, Horsham, Susse.x, collected by 
Mr. T. 8. Hillman, and showing the simple intestinal coiling of'a predacious species. 
feature alone. The intestinal canal of the strictly predaceous species 
has always a much simpler and shorter course, Imt is ecpially adapted 
to file nature of the food upon which the creature naturally subsists. 
This portion of the alimentary tract lias pi’incipally an absorjitive 
and excretory function, although intestinal digestion is also carried 
on along the greater part of its course. It terminates at tlie 
anus, which is of ectodennic origin and primitively placed at flic 
posterior end of the body, but in the Anisopleurous Gastropods 
the torsion of tlie visceral sac, due to the development of a heavy 
univalve shell, has, generally speaking, transferred the orifice towards 
the front, with the re.siiii-atory and other apertures with which it is 
usually associated. 
