182 IANTHTNID.E. 



approaches that of the waters of the open sea as to 

 render it almost invisible, except at close quarters — as, 

 for instance, from the gunwale of a boat. Mr. Benson 

 (Ann. & Mag. N. H. 3rd ser. vi. p. 405) compares the 

 float, seen under these circumstances, to a minute flock 

 of cotton, broad at one end and pointed at the other. 

 It is still a question whether any species of Ianthina is 

 furnished with eyes. Risso describes the animal as 

 having " les yeux pedoncules ; " but his authority is not 

 infallible. Lesson and Rang also placed the eyes at the 

 points of the tentacular prongs j D'Orbigny at the outer 

 base of the tentacles. According to Arthur Adams, the 

 " eyes are very small and indistinct, and are placed on 

 a short peduncle on the outside of the conical tentacles."" 

 He, however, has since given a different account, as fol- 

 lows : — " The animal is entirely blind. I sought in vain 

 for eyes, both at the base and apex of the longer, ex- 

 ternal, pointed tentacle, and likewise at the truncated 

 apex of the inner and shorter tentacular process. No 

 trace of eyes was visible, although an accidental dark 

 round spot of pigment may have been mistaken for 

 these organs/' My own examination of specimens, 

 preserved in spirits, of I. communis and /. globosa induces 

 me to agree with the last observation : I could not detect 

 any vestige of eyes. The habitat of the Ianthina is de- 

 termined by the nature of its food, which principally 

 consists of Velella and similar animals. Coates indeed 

 found that some were cannibals, having in their digestive 

 tube shells of other Ianthina, whose diameter was three 

 times that of the oesophagus in its usual state. Its zoo- 

 phagous tastes appear to be even more varied. "Al- 

 though doubtless the chief food of Ianthina consists of 

 Physalice, Porpitce, and Velellae, which are usually seen 

 floating in its society, on the surface, in calm weather, 



