IANTHINA. 



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that the Ianthina held the Velella bv its mouth, not 

 unfrequently swallowing half of it ; he also on several 

 occasions discovered young Velella in the stomach of 

 an Ianthina. In 1776 the celebrated Eastern traveller 

 Forskal gave, among other interesting particulars of the 

 Ianthina, an account of its fry. The species which he 

 examined was evidently a viviparous one, /. communis. 

 He says that each of the fry has in front of its shell two 

 transverse roundish lobes (vela) , covered with vibratory 

 cilia, with which it rowed itself through the water. His 

 further statement that the float adheres to the mantle 

 of the animal, and his supposition that the ovary or 

 matrix is placed in the proboscis, are incorrect. The 

 figure given by Bosc is merely a copy of Colonna's ; he 

 hazarded the unwarrantable assertion that the Ianthina 

 absorbs the air contained in its float-cells and refills them 

 at pleasure. Admirable details of the anatomy were 

 published in the ' Memoires ' of Cuvier, who acknow- 

 ledged the aid he received in these investigations from 

 three zealous naturalists, MM. Homberg, Savigny, and 

 Peron. He regarded the float as the rudiment of an 

 operculum, transmuted by organic action; and he be- 

 lieved that the animal could withdraw it into its shell, as 

 well as that some individuals have naturally no float, or 

 that it is only developed at a certain age or at a parti- 

 cular season of the year. All these opinions would un- 

 questionably have been modified, if not renounced, by 

 the illustrious zoologist, had better opportunities oc- 

 curred to him of examining the organization of this 

 mollusk. Mr. Bennett tells us (Med. Gaz. 1834, p. 233) 

 that when the Ianthina was purposely irritated, it had 

 no power of withdrawing the float, which always remained 

 stationary, even when the animal retired into its shell. 

 Subsequent experiments have shown that this apparatus 



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