154 THE OCEAN WORLD. 



dages attached to the under surface of the Velella. The form of the 

 individuals is much more varied, inasmuch as they are extremely 

 contractile. Nevertheless, they have considerable resemblance to 

 the corolla of a hyacinth. 



These reproductive individuals are at the same time nurses. 

 The Medusas originating by budding in the case of these reproduc- 

 tive individuals, constitute the sexual state of the Velellae. They 

 exist, in short, in two alternate states : the one sexual, producing 

 eggs ; in this state they are isolated individuals of the Medusidae, 

 which never group themselves or form colonies ; the other aggregate 

 state is non-sexual, and in it they form swimming colonies, under the 

 special designation of Velella. 



The genus Velella, so called by Lamarck, is found widely diffused 

 in the seas of Europe, Asia, America, and Australia. One species, 

 V. spirans, is often taken on the southern coasts of England and 

 Ireland. The animals are also met with far out at sea, and often 

 collected together in considerable masses, old and young together. 



Such is a brief account of the strange facts to which the careful 

 study of these lower animals initiates us. 



In the genus Rataria the body is oval or circular, sustained by a 

 compressed sub-cartilaginous framework, much elevated, having a 

 muscular, movable, longitudinal crest below, and provided in the 

 middle with a free proboscidiform stomach and a single row of 

 marginal tentacular suckers. De Blainville was inclined to consider 

 the very small animals which Eschscholtz termed Ratarice as young 

 and undeveloped Velella. M. Vogt sets the matter at rest that the 

 Rataria are the young of Velella^ which have acquired, by little and 

 little, the elliptical form, but that the limb is only furnished at a later 

 period to the reproductive individuals. These Ratariae are engen- 

 dered, according to Vogt, by the naked-eyed Medusae born of the 

 Velellae, and owe their existence to the eggs produced by these 

 Medusae. 



The second genus Porpita consists of colonies of floating animals 

 furnished with a cartilaginous, horizontal, and rounded skeleton, but 

 they are destitute of crest or veil. The body is circular and de- 

 pressed, slightly convex above, with an internal circular cartilaginous 

 support, having the surface marked by concentric striae crossing other 

 radiating striae, the upper surface being covered by a delicate mem- 

 brane only. The body is concave below ; the under surface is 

 furnished with a great number of tentacles, the exterior ones being 



