CHAPTER LXI: THE NAKED SEA SLUGS 

 Sub-Order Nudibranchiata. 



Shell wanting in adults; no proper gills nor osphradium; 

 body soft, worm-like, with many and elaborately branched 

 tentacular processes, called cerata, on the back and sides; skin 

 stiffened by spicules of lime; jaw and radula usually present. 



Mollusks live in shallow water, gliding about on stems of sea- 

 weeds, feeding on algae, mollusks or anemones, swimming, foot 

 upward, with an undulating motion. 



There is not room in a general book on mollusks to des:ribe 

 in detail the families of the sea slugs. A few typical examples 

 must suffice. 



The Plumed Sea Slug (/Eolis papulosa, Linn.) is one of 

 the most familiar sea slugs on the North Atlantic shores, American 

 and European both. The back is covered with elongated papilla;, 

 like tubular fringes, that fall away from the median line. The foot 

 is squared in front and tapers to a point behind. The head bears 

 two pairs of tentacles. The plumes serve a four-fold purpose: 

 (i) they are breathing organs; (2) they contain stinging threads 

 that the asolis shoots out at any creature that molests it; (3) 

 they contain branches of the liver, and so help in the digesting 

 of food; (4) they resemble the tentacles of the cave-dwelling 

 anemone (Sagartia) which is distasteful to fish, and thus earn, by 

 deception, immunity from attack. In an extremity, the /^olis 

 flings off a bunch of its plumes, and escapes while its pursuer 

 is examining them. It is a small matter to grow new ones in 

 their places. 



This creature glides rapidly among seaweeds, or swims in 

 clear water, a thing of grace and beauty, taking on the colours of 

 the anemones and algse it feeds upon. Its usual colouring is 

 yellowish gray to orange, with spots of green and purple. The 

 /Eolis is a bold creature, never seeming to hide, but evidently 

 trusting that memory of one stinging, bad-tasting sample mouth- 

 ful is sufficient to deter a fish from attacking it. The bright 



248 



