HELIX POMATIA. 



tentacula can be drawn inwards by a process resembling the 

 reversion of the finger of a glove. On the back, a turbinated 

 calcareous shell of sufficient capacity to allow the whole body 

 of the animal to be lodged in its interior. 



NATURAL HISTORY 



The common garden snail of this country, and the edible 

 snail of Europe, are well-known examples of a family of ter- 

 restrial and air-breathing Gasteropoda. In tropical climates, 

 however, more striking ones are to be found. They are 

 equally adapted to the hottest and the coldest climates, the 

 most cultivated and the most barren situations. The work of 

 Dr. Pfeiffer is the latest and the most elaborate on this group. 

 In the works of Wood, Sowerby, Reeve, and others, a great 

 number of species are figured. An inspection of the cases 

 containing them in the British Museum will show how varied 

 their forms are, and how beautifully colored are many of the 

 species. There are some brought from the Philippine Islands, 

 by Mr. Cuming, which when wet lose their color, but regain it 

 when dry. This is owing to the nature of the epidermis. 



The garden snail, Helix aspersa, and its allies, constituting 

 the family Helicidce, are closely allied to the slugs in organi- 

 zation, and differ from them in little else than in their being 

 inclosed in a shell, which is univalve, spiral, sub-pellucid, and 

 brittle, and has a semilunar aperture. Its head is furnished 

 with four tentacula ; on the superior pair the eyes are placed, 

 while the inferior pair have no visual organs, but seem more 

 exclusively adapted to the perception of tactile impressions. 

 Both the upper and lower tentacula are retractile, and can be 

 completely inverted, so as to be withdrawn into the interior of 

 the body. Each tentacle is a hollow, flexible cylinder. When 

 partially retracted, the extremity of the organ is drawn in- 

 wards, and two cylinders are thus formed, one within the 

 other ; if the outer cylinder is elongated, as in protruding the 

 tentacle, it is at the expense of the inner one, and, on the con- 

 trary, the inner cylinder, when the organ is retracted, is length- 

 ened as the other becomes shorter. Snails are hermaphro- 

 dites, and consequently they are all capable of laying eggs, 

 which they carefully bury in the ground. These eggs are very 

 numerous, and there have been found eighty in one heap. 

 They are round, semi-transparent, about the size of a small 

 pea, and covered with soft shells ; they are also united to each 



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