MOLLUSCS. 



99 



fondness for a vegetable diet frequently renders them a pest in market 

 gardens, and at times they have been so abundant and so destructive in 

 Europe, that the power of the Church has been invoked, and by papal bull 

 they have been excommunicated along with comets and other foes to 

 mankind, which, of course, at once checked their ravages. 



Snails do not make very attractive pets, since they are almost wholly 

 lacking in intellect, and yet one by watching them can make numbers of 

 interesting observations. They thrive well, and by feeding them with 

 leaves, etc., one can readily see the way they eat and watch the operation 

 of the lingual ribbon described on a preceding page, while by placing one 

 on a bit of glass the peculiar processes involved in walking are easily seen. 



Fig. 93. — Agate-shell (Acho.tina). 



A few species of snails are used for food, and have been for thousands 

 of years. The Romans bred them for the table, as do the French to-day. 

 In France they are highly esteemed, but the English-speaking races, for 

 some reason or other, do not take kindly to them. Some are imported 

 from France, but it is impossible to obtain any statistics of the amount, 

 for in the custom-house reports they are included under the head of ' fancy 

 groceries not otherwise provided for.' 



In the tropics the species of Helix and its allies are enormously devel- 

 oped, both in species and in individuals. Here grow huge Bulimi and 

 Achatince, some of which lay eggs as large as a pigeon's, while in some of 

 the islands of the South Seas the variety of forms is almost incredible. 

 Thus the Hawaian Islands are filled with varieties of the beautifully 



