Sea-slugs 285 



trusting no doubt to the anemone-likeness, coupled 

 with the knowledge of anemones that must pervade 

 the waters — it being sufficient to resemble an anemone 

 in order to discourage would-be destroyers, for the 

 anemones are known to have stinging powers, a 

 tenacious hold, great storage capacity, and a bad 

 taste. Idaliiut buries itself in the bodies of Simple 

 Ascidians {Cynthia), protruding its tentacles and 

 filaments in a very anemone-like manner. Alder 

 and Hancock, who never suspected the object of the 

 remarkable forms and colour-ornamentation of the 

 Sea -slugs, describe the discovery of the species. 

 They say : — 



" This valuable addition to our Fauna was dredp-ed 

 m the summer of 1853, near Castle Cornet, in 

 Guernsey. From a curious habit, hitherto unknown 

 in this tribe, of concealing itself in the test of an 

 Ascidian (Ci/nthia tiiherosa), it escaped observation 

 on being taken from the dredge, and was put into 

 our collecting- box as an Actinia [anemone] partially 

 expanded. On examining the contents of the box in 

 the evening, we were delighted to find we had got a 

 beautiful Idalia, which had crept so far out of its 

 place of concealment as to display its true form. A 

 second individual was afterwards found amongst the 

 contents of the box, with only its head and anterior 

 filaments protruded from the test of another 

 Cynthia of the same species." There are five other 

 native species in this genus. 



The Crested Slug (Ancida cristata) appears, like 

 Idalina, to carry a little anemone on its back. It is 

 not more than 1 inch in length, transparent white 

 except the sense-organs {rhinopl tores), and the tips of 



