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The polypestock of the beautiful Velella, or sail-siphonophore, 

 forms a cartilaginous ball, on the underside of which sit the 

 single individuals, while on the upper side is a thing like a 

 sail, which aids the progress of the colony swimming close to 

 the surface of the water. 



Ctcnophores or Bib-jcllyGsli. 



The Ctenophores are as transparent as the medusae, a quality 

 possessed by many marine animals. There are very many trans- 

 parent mollusks, and even transparent worms, crabs and fish, 

 as we shall see later. The reason of this property is probably 

 to be sought in the protection it affords to these animals , 

 the ease with which they can both avoid their enemies and 

 catch their prey. For all these delicate creatures are cruel 

 robbers, and devour animals the very contact with which we 

 should think would be sufficient to annihilate them. But their 

 terrible nettle-cells enable polypes and medusae to kill much 

 larger animals than themselves, and one may very often see 

 a small fish in the stomach of the delicate a medusa, which 

 completely dissolves and digests it. 



The shape of the Beroe and Cydippe (both Ctengplwres) is 

 like a barrel, the long remarkable Venus-girdle (Cestus Ve- 

 neris) is like a ribbon. These three species are often found 

 in the tanks , and attract the attention of the visitor by the 

 rainbow-coloured waves that seem to run along their bodies. 

 These waves of colour are produced by rows of very delicate 

 oar-plates that lie in great numbers close together , and are 

 almost constantly in rapid motion, which breaks the rays of 

 light and causes the appearance of the prismatic colour. 



The zoological Station may well be proud of its exhibition 

 of the marine animals now mentioned. The southern position 

 of Naples and the situation of the Aquarium close to the sea, 

 give the latter this valuable monopoly. Succesive days of calm 

 and fine weather during spring and autumn enable the fisherman 

 to catch these rare and beautiful animals. They die, however, 

 very soon, the Sinophophores especially scarcely lasting a day. 



The animals hitheito mentioned are scientifically classed 

 under one type , which bears different names, but is oftenest 

 described under that of the Coelenterata given by Professor 

 Leuckart. 



The animals we shall now describe used to be included with 

 them under the common name of Radiata, but later research 

 has proved that they are very different. These are the 



