IANTHINA. 183 



yet an occasional Barnacle does not seem to come amiss 

 to the blind Snail of the Ocean. From the stomachs 

 of several I extracted fragments of the tufted feet of 

 Lepas ; and in one which I examined the Z/?/ms- remains 

 occupied the entire length of the oesophagus/' (A. 

 Adams.) Mr. Benson says that when the snout is pro- 

 truded, the flexible cilia round the mouth are extended 

 and agitated with great rapidity, apparently in search 

 of food. The top of the living shell is now and then 

 crowned with a cluster of Lepas pectinata or of L. fas- 

 cicularis. I may also mention, on the authoritv of Mr. 

 Benson and Dr. Wallich, that the float is often infested 

 with a small swimming crab of a brilliant blue colour 

 like that of the shell ■ this uses the float as a raft. 



The sexes of Ianthina are separate. Fritz Muller has 

 minutely described the spermatozoa of the male, which 

 are clothed with long delicate microscopical hairs or 

 filaments, forming a swimming-apparatus. As in Litto- 

 ritia, so in the present genus, some species are oviparous, 

 and others viviparous. In the former case the eggs, 

 when excluded from the ovarv, are enclosed in cells, and 



v y y 



attached (probably by the foot of the parent) to the 

 under side of the float, from which they hang thickly 

 but separately. Achille Costa computed the number 

 produced in the breeding- season by each individual at 

 no less than a million. Owing to the pelagic and wan- 

 dering habits of the animal, its own float would certainly 

 be the best nidus it could have, if indeed anv other were 

 at hand at the time of parturition. Professor Costa 

 (not Achille) erroneously stated that the egg-cases at- 

 tached to the float belong to another mollusk. It re- 

 minds one of the famous controversy, which so long 

 disturbed the peace of conchologists, about the supposed 

 parasite that inhabited the shell of Argonauta, and (cue- 



