558 THE INVERTEBRATA 



The buccal cavity is succeeded by the oe^phagiis, which widens 

 out into the crop, which in Hfe contains a brown hquid secreted by the 

 'Miver". On the side of the crop are the branching white salivary 

 glands, which empty their secretion by two ducts running forward 

 into the buccal cavity. The secretion is partly mucus, partly digestive 

 fluid containing an enzyme acting on starch. The crop is succeeded 



:ped.(i. 

 muc.gh 



Fig. 382. Helix pomatia. A, Section of alveolus of the digestive gland. 

 ab.c. absorptive cells; cal.c. calcareous cells; cil.c. ciliated cells of liver tube; 

 f.c. ferment cells. After Meisenheimer. B, Diagrammatic side view of animal 

 dissected to show the alimentary canal and nervous system. Original. An. 

 anus; ao. aorta; au. auricle; buc. buccal mass; biic.g. buccal ganglion; ce.g. 

 cerebral ganglion ; cr. crop ; dig.gl. digestive gland ; d.d. openings of digestive 

 ducts (the ducts represented by black lines); F. foot; h.gl. hermaphrodite 

 gland; int. intestine; k. kidney; muc.gl. mucous gland; n.n. nerve net in 

 surface of foot; oc.ten. oculiferous tentacle; ot. otocyst; pa.g., ped.g., pl.g. 

 parietal, pedal and pleural ganglia; pal.n. pallial nerve; rad.s. radula sac; 

 sal.d. salivary duct ; sal.gl. salivary gland ; spt. spermatheca (duct broken off 

 short) ; st. stomach ; va. valves directing food into digestive ducts ; ven. 

 ventricle; vis.g., vis.n. visceral ganglia and nerve. 



by the stomach; this is imbedded in the digestive gland (liver), which 

 occupies most of the visceral hump. The ** liver", though apparently 

 solid, is composed of a number of tubes and the end portion {alveolus) 

 of each tube is glandular; the rest is ciliated and serves to introduce 

 small fragments of food into the active alveolus. The alveoli contain 

 cells of three kinds, secretory, resorptive and lime-containing (Fig. 



