LUCEENARIANS OF PORT ERIN. 155 



ment of tentacles having been disposed of as far as the 

 groups of secondary tentacles were concerned (as detailed 

 above), there only remained the octagonal disc and absence 

 of primary tentacles in Depastriim to separate it from 

 Carduella. 



With regard to the first point, as Clark points out, 

 there is in Sars' figures (and in Allman's also) an octa- 

 gonal area, the corners of which correspond to the inter- 

 vals between the tentacular groups and whose outline is 

 marked out by a distinct line of brown pigment ; the ten- 

 tacles arise from immediately without this line, and there 

 can be little doubt that this is the octagonal margin o 

 the disc spoken of by Gosse, but the real margin of the 

 disc is formed by the circular muscle situated outside the 

 origin of the tentacles, some of which are usually curved 

 over it when the animal is fully expanded, the primary 

 tentacles being invariably so apparently. This circular 

 muscle is in life a delicate translucent structure and may 

 have escaped Gosse's notice. Then as to the absence of 

 primary tentacles in Depastriim. These in Carduella are 

 similar in form and structure to the secondary tentacles of 

 the groups, unlike those oi Haliclystus auricula which 

 have been modified into the so-called marginal anchors 

 and function as adhesive organs. They are in Carduella 

 not very conspicuous, being usually somewhat smaller 

 than the secondary tentacles and constantly (as I have 

 remarked above) reverted over the circular marginal mus- 

 cle and closely applied to its surface. It is accordingly 

 not unlikely these too escaped Gosse's observation, espe- 

 cially if his specimens had been kept long, as the tentacles 

 seem apt to slough away when the animal is removed 

 from its natural conditions. In addition I may mention 

 that Depastrum, and apparently other members of this 

 group also, is subject to much variation, especially in 



