A BLACK DORIS. 229 



to me that on the Frith of Forth, at least, vast 

 numbers of these animals do not long survive the 

 hatching season. 



Whether this be the case or -not, it is a most 

 singular fact that in this locality, a Doris more than 

 one or two inches in length is scarcely ever to be 

 met with. 



There is at present in one of my tanks a specimen 

 of the Doris of a pearly- white colour, a second, tinted 

 white and pink, and two others which are quite 

 black, all being procured from the coast near Edin- 

 burgh. The last-mentioned animals are, I think, 

 somewhat uncommon. When watching one of them 

 in motion while the sun is shining down upon it, 

 the hue of the creature changes from a black to a 

 very deep purple, owing, no doubt, to its fleshy disc 

 being many shades lighter than its body, which, 

 being extended, and exhibited under a full glow of 

 light, becomes semi-transparent. This peculiarity is 

 not evident, of course, when the Doris is lying in a 

 passive state, with all its gill-plumes closed up. 



This sombre-coated gasteropod, although rare in 

 some localities, is very plentiful in foreign parts, if 

 the following may be received as an accurate narra- 

 tive. ' On a reef of rocks near the island of Raiatea 

 is a huge unshapely black or brown dug, here called 

 * Biche,' from six to seven inches long, and five to 

 six broad. Is is caught in vast quantities, and not 

 only regarded as a great delicacy by the natives, 



