CLAIIS, OYSTERS, AXD JIUSSELS 



117 



as Limax (Fig. 64). It is dark in color, with two large 

 tentacles on its head, and if looked at closely, will be found 

 to carry a dark, fleshy cape, the mantle, just back of the 

 head. Some slugs leave a white, shining streak wherever 

 they go, owing to the fact that they give out a mucus which 

 hardens m the air. This is done to make a soft silky path 

 over sand antl ashes or other harsh substances that would 

 irritate the body. They may be traced long distances and up 



■ JIN«s 



Fig. 64. — Slug (Limax) : o, opening to the lung; c, mantle. 



trees, by this shining streak. When ready to descend from 

 the trees, some species spin out a thread of the mucus, like 

 a spider, and drop down by means of it, insteatl of retracing 

 their path. They often occur in such numbers as to be 

 injurious to garden vegetables. 



Sea slugs. — There is a group of marine moUusks, kno'mi 

 as the nudibranchs, that have no shells in the adult stage, 

 hence are often called sea slugs or naked mohusks. The 

 gills of these moUusks are usually arranged in tufts that 

 project from the sides or back of the animal. The sea slugs 

 are of various and striking colors, and vary greatly in shape 



