SHELLS OF COMMOX OCCUREEXCE, 



EY WILLIAM WALLACE FYFB. 



The LimacidcVj or land-slugs, are represented con- 

 ecologically by tlie tliin crustaccoiis sliells found on 

 dissection witliin their mantles, being, as every- 

 body fiimiliarly knows, outwardly destitute of shell. 

 This shield is protective of the cavity employed in 

 respiration. Figs. 1, 2, 3, and 4 represent four of 

 these shields, extracted from the milky, yellow, 

 tree, and spotted slugs respectively (Limax agrcstis, 

 L.flavxis, L. arhorumj L. cinereus). 



These creatures, as every lover of a garden too 

 well knows, are powerful vegetable feeders, making 

 their appearance in damj^ weather in multitudes 

 like an Egyptian plague. Their destructive voracity 

 enables them to secrete an exuberance of white 

 milky mucilage from their bodies, to discharge this 

 copiously when irritated, and to mark their devour- 

 ing tracks in their slime. Like linseed and other 



