SECT. XI. 



NAKED MOLLUSC A. 



241 



of the back, leaving a space between them, as in fig. 

 175. They are covered with long cilia, whose vibra- 

 tions send a perpetual current of sea-water along each 

 of them, the respiration is aided by vibrating cilia, scat- 

 tered almost over the whole body, and the circulation 

 of the blood is very simple. 



The Eolis has a head prolonged into a pair of tenta- 

 cles which are active and as sensitive as antennae. 

 Another pair on the back have ten or twelve narrow 

 plates twisted in a spiral round them ; the eyes are at 

 the base of these horns. The mouth contains horny 

 jaws and a spiny tongue like a mere strap covered by 

 numerous transverse plates armed with recurved spines 

 not more than a sixth part the thickness of a human 

 hair. Fig. 1 76 repre- 

 sents the tongue and 

 some of the spines 

 greatly magnified. 

 The mouth leads in- 

 to a short and large 

 membranous sto- 

 mach, from each side 

 of which branches 

 are sent off, from 

 whence long canals 

 traverse the papillae 

 longitudinally, and 

 perform the part of 

 a liver. In many 

 species these tubes 

 are brilliantly co- 

 loured, but none are 

 more beautiful than 

 those in the Eolis 



coronata, which is found under stones, like a mass of 

 jelly, not larger than a pea, at low spring tides, on 



VOL. II. R 



Fig. 176. Tongue-teeth of Eolis coronata. 



