148 Mr. E. Forbes on two Species of CydX^^^e. 



it, retracting and extending them alternately. They seem to 

 guide it in its course. Not unfrequently it remains some time 

 at the top of the water ; and when it wishes to descend, turns 

 over, drawing up its filaments suddenly, and then swims 

 mouth downwards to the bottom of the vessel. 



Imbedded in the substance of one of these animals, near the 

 stomach, is a remarkable parasitic worm, in shape resembling 

 a Filaria. The only specimen in which the parasite was found 

 is now preserved in Mr. Goodsir's collection. 



The comparison of the two species of Cydippe here described 

 induces me to regard the filamentary cavities and the filaments 

 themselves as the generic points of their organization; while 

 the number of rows of cilia, the length of the ciliferous ridges, 

 and the relative proportions of the various parts of the ani- 

 mals afford good specific distinctions. The character of the 

 genus given by Blainville, *^ Actinologie,' p. 148, abounds in 

 errors, being founded on the imperfect observations and rude 

 sketches (chiefly of travellers) published before his book came 

 out. Thus the filaments are represented as proceeding from 

 the mouth, and the body of the animal as divided into eight 

 lobes by the ciliferous ridges, whereas the ridges are really 

 placed on the summits of the eight lobes. The fragility of 

 the animals and the unfavourable circumstances under which 

 they have generally been observed easily account for these 

 mistakes. The observations of Otho Fabricius on this Bero'e 

 ovum [Mertensia ovum. Lesson), of Dr. Fleming on his Bero'e 

 ovatus, ^ Wern. Mem.^ iii. 401, and of Dr. Grant on Cydippe 

 pileus, ^ Zool. Trans.^ vol. i. are most important of any on this 

 tribe of animals. 



Lesson, in his ^ Memoire sur la Famille des Beroides,^ (An. 

 Sc. Nat. 1836), divides the genus Cydippe into three genera; 

 Eucharis, Eschscholtz; Cydippe, Eschscholtz; and Merten- 

 sia, Lesson. Of Cydippe, to which both the species I have 

 described belong, he enumerates two species, Cydippe pileus 

 and Cydippe densa, the latter a Mediterranean animal having 

 red filaments. The only recorded British species is the Beroe 

 pileus of authors, Pleurobranchia pileus of Fleming, Cydippe 

 pileus of Eschscholtz, Blainville, and Lesson. To it the first 



