no THE MOLLUSCA 



It was concluded that the snail had deserted its weakly mate, 

 but after twenty-four hours it returned, and apparently com- 

 municated the results of its expedition, for in a short time both 

 started off along the same track and disappeared over the wall. 



The muscular strength possessed by snails is really remark- 

 able. A naturalist carried out some experiments on a Snail (Helix 

 aspersa) weighing J oz. He found " it could drag vertically a 

 weight of 2j oz., or nine times its own weight. Another Snail, 

 weighing J oz., was able to drag in a horizontal direction, along 

 a smooth table, twelve reels of cotton, a pair of scissors, a screw- 

 driver, a key, and a knife, weighing in all no less than 17 oz., or 

 more than fifty times its own weight." * 



Snails and slugs have the power, in common with many other 

 molluscs, of reproducing lost parts. The loss of a tentacle or part 

 of the foot is no very serious matter to these strange creatures, 

 for in a short time it will have grown again. During hibernation 

 no new growth takes place ; and if a snail meets with an injury 

 just before its dormant period, this will remain in the same state 

 until the animal returns to activity, when the healing process 

 will at once commence. 



True Snails (Helicida) are found in nearly every part of the 

 world, and in almost every kind of situation, from the sea-level 

 to an altitude of 12,000 feet. Many are remarkable for the beau- 

 tiful colouring of their shells. The Giant Snail (Achatina fulva) 

 of East Africa is over 8 inches in length from the tip of its horns 

 to the apex of the shell, and its eggs are as large and as hard as 

 pigeon's eggs. Other species, quite as large, are found in South 

 America. 



The Scaphopoda differ from other molluscs in having a long, 

 tubular shell, open at both ends, very much like the shelly tubes 

 formed by certain species of marine worms. To this order belong 

 the Tooth or Tusk Shells (Dentaliida), of which two species are 

 found in Great Britain. These molluscs have no eyes, no tentacles, 

 and no distinct head, no heart and no gills; and respiration is 

 carried on by the walls of the mantle. They have a long, narrow 

 foot ; with this they burrow in the sand in which they live and 

 find their food. This consists of foraminifera and minute bivalves, 

 for although the Tooth Shells have no head they possess a mouth, 



1 Sandford, Zoologist, 1886, p. 491. 





