Sea-slugs 293 



back is coloured pale red, and the very worm-like 

 cerata are sage-green tinged with red and spotted 

 with white. 



The Dwarf ^olis {Cutltona nana) is only a few 

 lines in length, pale buff on the back, the liead and 

 tentacles white. The cerata are also white, but the 

 central tube is red, and a rosy tint shows through ; 

 they are arranged in eight or ten close rows. Like 

 other species, it is very sensitive, and when alarmed 

 brings its head and tail together, and so assumes an 

 anemone - like aspect. The Orange - tipped ^olis 

 {G. auixnitiaca.) is similar, but larger, attaining a 

 length of half an incli. It has a buff coloured back, 

 and the cerata are in about ten rows. The tips of 

 the latter are coloured brig-ht orang^e, below which 

 there is a white belt, and then the purple-red of the 

 central tube shows through the transparent re- 

 mainder. This lower portion is subject to much 

 variation of tint, probably due to differences of food. 

 It has been found from Shetland to Cornwall, feeding 

 on Tiihularia, etc. 



The Green ^olis (Cratena viridis) is entirely 

 tinged with green, though it is not so distinctly 

 green as some other species. The long slender body 

 is white with a yellow - green tinge. The cerata, 

 which are arranged in nine or ten rows, have pointed 

 white tips, the central tube being some shade of green 

 with darker spots. The first four rows of cerata 

 come close together, the other rows are quite distinct 

 one from the other. It feeds on Sea-mats {Flustra), 

 Lobster-horn (Antennularia), etc. We have no less 

 than thirteen representatives of the genus Cratena. 

 Of these 0. amoena might easily be mistaken for 



