24: FRIENDS WORTH KNOWING. 



Mountains. At any time, nevertheless, an artificial raising 

 of the temperature breaks the torpor, the warmth of the 

 hand being enough to set the heart beating. Extreme 

 drouth also will cause snails to seal their doors hermetically, 

 without even hanging a card -basket outside. This is to 

 shut off the evaporation of their bodily moisture, and hap- 

 pens in midsummer; hence it is termed aestivation. Cer- 



AN EDIBLE SNAIL. 



tain foreign slugs (Testacellidse) which have no shells, are 

 able to protect themselves under the same circumstances 

 by a gelatinous appendage of the mantle, which, in case of 

 sudden change of temperature, can be extended like an 

 outer mantle, so to speak, from its place of storage, un- 

 der the "buckler," and having wrapped themselves, they 

 burrow into the soil. These carnivorous testacelles are 



