KEPOKT ON THE ACTINIARIA. 17 



but by mucous cells, and nematocysts, and to entirely obliterate the sucking papilla' from 

 the list of systematic characters. 



With regard to the cinclides or pores of the wall, which are so extensively used 

 not only by Ehrenberg (Abhandl. d. Berliner Acad., 1832, Phys. CI., p. 225), but 

 also by Gosse, and still more by Milne-Edwards, I need only repeat what has been 

 already said. They are only distinct in a few forms, are questionable in most cases, 

 and therefore form a characteristic which is practically of no great use. The tentacles 

 form a much more important characteristic than the two already discussed, less on 

 account of their form and size, on which Ehrenberg lays such stress, than on account of 

 their arrangement and relation to the intraseptal spaces, which have hitherto only excep- 

 tionally been taken into consideration. 



Ehrenberg's system was first essentially improved by Milne-Edwards and Gosse. 

 Milne-Edwards added, to those already made use of by Ehrenberg, some new systematic 

 characters, which undeniably indicated progress. The extended knowledge of species 

 which had meantime been acquired rendered it necessary to take the different nature 

 of the pedal disk in the Minyadinse, Cerianthidae, and Ilyanthidse into account in the 

 formation of the system ; we owe to a more exact anatomical knowledge the apprecia- 

 tion of the systematic value of the marginal spherules. On the other hand, it is difficult 

 to understand how Milne-Edwards came to found tw r o great groups, " actinines vulgaires " 

 and " actinines verruqueuses," on such a character as the papillose or smooth nature of 

 the surface of the body, which is in itself unimportant and in no case clearly marked. 

 His mode of expression is by no means well chosen with regard to another point. 

 When, for instance, Milne-Edwards divides the tentacles into retractile and non- 

 retractile, he lays stress upon a secondary point, and overlooks the much more important 

 behaviour of the upper margin of the wall wdiich can be drawn over the oral disk in 

 the former case but not in the latter. This varying action of the wall is the only point 

 of importance, because it is anatomically founded on the structure of the circular muscle. 



What I have said about Milne-Edwards is also true, on the whole, of Gosse, as the 

 same distinguishing characters recur in his system, although he uses them in a <1 liferent 

 manner ; in consequence of this last circumstance the genera of Gosse and Milne-Edwards 

 are often not co-extensive. A step in advance is made, inasmuch as Gosse takes into 

 consideration in his descriptions the acontia, which he himself had discovered, but, <>n 

 the other hand, the inconsistencies of which he is guilty lay the English naturalist 

 open to the gravest criticism. How, for example, does it happen that the smooth 

 wall not pierced by cinclides is made the most important character of the Antheadse, and 

 in spite of this the genus Aiptasia, which has been separated from other genera chiefly 

 on account of the presence of cinclides and acontia, is placed in this family ? How can 

 the genus Phymactis, whose diagnosis rests upon the character " skin watted," be placed 

 among the Actiniadae in which the wall ought to be smooth ? 



(ZOOL. CHALL. EXP. — PART XV. — 1882.) P 3 



