212 GENERAL ZOOLOGY 



max'imus. It is a native of Europe, not of America, and 

 since its introduction here has become a more unwelcome 

 guest in greenhouses than any other species of slug or snail. 



In brief terms we may describe a slug as a snail with a 

 rudimentary shell. The elliptical plate of muscle on the dor- 

 sal surface of Limax is all that is left of the mantle. In the 

 process of degeneration, which we may well suppose has 

 occupied thousands of years, the mantle folded back over 

 the shell as the latter decreased in size. If we examine the 

 interior of the mantle, we find a thin, calcareous plate, which 

 is the rudimentary shell. 



The ravages of Limax maximus are not serious if the 

 florist does not allow refuse to collect about his buildings. 

 Many adopt the method of scattering ashes or cinders about 

 the plants to be especially protected. A slug crawling into 

 such an obstruction is stimulated by the dryness of the 

 ashes, or the roughness of the cinders, to secrete mucus from 

 the glands that occur in the skin. This mucus is like that 

 which is secreted from its foot-gland while crawling. Owing 

 to the unusual amount of mucus given off at such times, the 

 animal dies from exhaustion, and from suffocation by the 

 drying of its skin. 



Garden slugs that live out of doors burrow into the ground 

 and curl up when the coldest weather comes. Those in green- 

 houses remain active throughout the year. 



Several other slugs, some of which are smaller and much 

 more widely distributed than Limax maximus, occur under 

 logs and damp leaves. At times these become numerous 

 enough to do considerable damage in gardens. 



The Oyster Drill. A few minutes' walk along almost any 

 pebbly beach between Florida and the Gulf of St. Lawrence 

 would afford a collector the opportunity of observing the 

 subject of this description, the oyster drill (Urosal'pinx ci- 

 ne' rea, Fig. 119). In such a walk the artist discovered the 



