Sea-slugi 



291 



going on in their outer 

 layers, but their centres are 

 iilled with isolated portions 

 of liver directly connected 

 to the stomacli, whence par- 

 tially digested food is sent. 

 At the tip each of these 

 cerata is pierced, and through 

 the minute channel the JEoUs 

 ejects stinging threads for 

 the annoyance of such 

 creatures as would essay to 

 experiment upon the food 

 value of the slug. A fourth 

 use of the cerata is found 

 in their power to mimic the 

 tentacles of the Cave-dwell- 

 ing Anemone (Sagartia 

 ivoglodytes). Further, when 

 the ^olis is molested it can 

 throw off some of its cerata 

 to occupy — and probably 

 disagree with — its enemy ; 

 this appears to entail little 

 or no injury to the slug, for 

 the place .of the missing 

 cerata is soon taken by 

 newly-grown ones. M. Giard 

 has observed, at Wimereux, 

 how closely this species re- 

 sembles the Cave-dwelling 

 Anemone, but it is difficult 

 to say which is really the species that profits most by 



Plumed /€oli 



