EDIBLE SNAIL. 



117 



and albuminous bodies. In Helix the granules are clear yellow in colour ; sometimes, 

 as in Arion, they are the only coloured constituent of the cells. These granular 

 cells are absent in Cephalopoda. The ferment-cells vary in appearance in different 

 Mollusca. They are absent in Chiton, Patetta, Fissurella, and Pteropoda ; doubt- 

 fully present in some azygobranchiate Gastropoda and some Lamellibranchiata. 

 In shape they are like a club or pear, with the larger end turned towards the 

 cavity of the acinus. They contain each a vesicle inclosing more or less coloured 

 fluid, viscous or semi-solid bodies, fat and albumen globules. The refractile index 

 of the contents of the vesicle is low in Helix and Cephalopoda, and their colour is 

 similar to that of the granule-cells. It is generally more or less different in the 

 Opisthobranchia and Azygobranchia. It is similar in intensity in Pulmonata, more 

 intense in other groups (Frenzel). The calcareous cells are wanting in Lamellibran- 

 chiata, Pteropoda, and in Natantia (= Heteropoda) among Gastropoda, and other 

 isolated instances in this Class. Their size is great, and they are more or less 

 triangular with the base external, and the apex not reaching the cavity of the 

 acini. They contain the so-called calcareous globules, which vary in chemical 

 characters. Lime is always an ingredient, and, according to Barfurth, in com- 

 bination with phosphoric acid, a view opposed by Frenzel. Barfurth has shown that 

 the percentage of inorganic ash obtainable from the liver of Helix pomatia varies 

 at different seasons. In May the amount averaged 20.24 per cent.; in September 

 25.72 per cent. ; after the breaking and repair of the shell it fell at once to 16.99 

 per cent. ; and after the formation of the epiphragma to 10.26 per cent., the 

 normal figure during the winter rest of the animal. It may be added that the 

 quantity of phosphates in the epiphragma is 5.52 per cent, as opposed to 0.85 

 per cent, in the shell. The mucus of Helix contains lime, and to a very large 

 amount in Arion. The secretion of the liver is acid, and has been found to 

 have a diastatic and a peptic action in H. pomatia. It contains enterochlorophyl 

 in Helix pomatia, in many other Gastropoda, some Lamellibranchiata, and haematin 

 in various Pulmonata, e. g. Helix pomatia, H. aspersa, and Arion ater, &c. Gly- 

 cogen is found in the liver ; in Helix, in the plasma-cells of the connective tissue 

 which are abundant; in Limax, in the liver-cells, the connective tissue being 

 scanty. For the distribution and mode of occurrence of glycogen in the other 

 tissues of Gastropoda, as well as in the tissues of other animals, the very valuable 

 paper of Barfurth's, A. M. A. xxv. 1885, should be consulted. 



The hermaphrodite gland or ovo-testis consists of a number of cylindrical 

 follicles opening into a common duct. The ducts from the various groups of 

 follicles unite in their turn with the chief duct of the gland, which is lined by a 

 non-ciliated squamous or columnar epithelium. The ova and spermatozoa are 

 formed from the lining epithelium of the follicles, but at a different time. The 

 albumen gland is a racemose gland. It opens by a common duct, which with its 

 branches is lined by a ciliated epithelium. The ovi-spermi-duct is lined by a 

 ciliated epithelium, and both portions are beset with glands. The free portion of 

 the oviduct is also ciliated, but not the vas deferens, as is the case also with the 

 penis and flagellum. The latter organ, with the hinder part of the penis, secretes the 

 ' capreolus,' or spermatophore, a structure formed of hardened mucus. It is more or 

 less elongated and its edges folded so as to form a groove in which a mass of 

 spermatozoa are lodged. In copulation it is transferred to the duct of the recepta- 



