2S LAND ANb FRESH-WATER SHELLS. 



food. In one stomach of the animal of this species I counted 

 no less than twenty-seven small pebbles. 



The " Mitteldarmdriise," as the organ has been called by 

 Frenzel, is a brownish mass divided into two asymmetrical 

 portions, and lying in the whorls of the spire. Known in English 

 works as the liver, hepato-pancreas, digestive gland, or gland of the 

 mid-tntesfine, its left lobe or portion is the larger, and is sub- 

 divided into three smaller lobes, from each of which a duct carries 

 the secretion to a common duct, which opens on the left side 

 of the stomach. It is grooved by the intestine, and occupies the 

 upper half of the first turn of the spire. The right portion, or lobe, 

 separated from the left lobe by four structures, the crop, 

 stomach, intestine, and albuminiparous gland, is placed in the 

 upper turns of the spire, and has imbedded in its substance the 

 hermaphrodite gland or ovotestis. It has a single duct, which opens 

 into the right side of the stomach, nearly opposite to the opening 

 of the duct of the left lobe. In microscopical structure it is an 

 acinous gland, the several acini of which are bound together by 

 connective tissue. The gland substance shows a differentiation 

 into three kinds of cells, calcareous cells, which are triangular, and 

 contain lime in combination, according to Barfurth, with 

 phosphoric acid ; * hepatic or granular cdls, containing fat globules, 

 albuminous bodies, and granules which are highly refractile the 

 fat globules are passed with the faeces ; ferment cells, which are 

 more or less club-shaped, and contain fat globules, albumen glo- 

 bules, and other bodies that are more or less viscous. The fat 

 globules blacken on treatment with osmic acid. The ferment cells 

 secrete a proteid-digesting ferment named trypsin, and also an 

 amylolytic ferment. In the " Mitteldarmdriise " of Arion ater, 

 Helix aspersa, and H. pomatia haematin has been demonstrated ; 

 and in the last named of these species enterochlorophyll has been 

 found in addition. According to Barfurth, the secretion of the cal- 

 careous cells goes in the main to the formation of the epiphragm. 

 He burnt the organ to an ash at different periods of the year, and 

 then quantitatively estimated the amount of lime it contained. 

 The average amount present in May was 20*24 P er cent., in 

 September 25-72 per cent., and after the formation of the 

 * This has been denied by Frenzel. 



