14 



A MANUAL OF AMERICAN LAND SHELLS. 



ing the shell-bearing species, and I shall therefore mention here only 

 those which are peculiar to them. They difier from the other families 

 in not possessing the faculty of hibernation, or suspension of their or- 

 ganic luuctions during the cold season. In temperate latitudes the 

 snails hibernate, under all circumstances, on the approach of cold 

 weather; the slugs, on the contrary, having the power of resisting ex- 

 treme cold, continue in their usual haunts until severe frosts set in, 

 ■when they retire into the earth and other sheltered retreats. Here they 

 remain in a state of inaction and partial torpidity; the functions of the 

 body, however, still going on, though slowly and with diminished force. 

 A slight increase of heat arouses them and stimulates their organs to 

 renewed action, and they accordingly often come abroad in mild weather 

 even during the winter. Those which inhabit cellars and other pro- 

 tected situations are in motion throughout the year; and individuals 

 of all the genera and species which I have kept in confinement have 

 continued active, fed freely, and increased in size as much in the coldest 

 months as in the summer. 



All the species which have yet come under my notice possess the 

 power of suspending themselves in the air by a gelatinous thread. This 



they eifect by accumulating a quantity of 

 tenacious mucus at the posterior extrem- 

 ity of the foot, which they attach to the 

 object from which they are to commence 

 their descent; then, loosing their own hold, 

 they hang suspended by this point. Con- 

 tinuing the secretion, their own weight 

 attenuates the mucous attachment and 

 draws it out into a thread. As this dries 

 and hardens, a fresh supply is afforded, 

 the thread is lengthened, and the animal 

 lets itself down any desirable distance. 

 At this time, also, the margin of the foot 

 Limax campestris. sna-pouded. pours out mucus freely, and duriug the 

 whole operation the locomotive disk is in active undulatory motion, in 

 the same manner as when in ordinary progression. It appears in this 

 way to guide and force towards the extremity the mucus which is se- 

 creted on its surface, and which, collected at its extreme point, forms the 

 thread. The slug often pauses in its descent, and extends its eye-pe- 



FlG. 1. 



