Details of Caslenterata. 65 



but the important parts of eacli organ, like the ridge of the crest, 

 the bases of the tentacles, and the thread-cell bearing ridges of the 

 tentacles, are also emphasized with deep colour. 



Yelella. This beautiful creature, which sometimes finds its way 

 to our shores, is like a crystal raft fringed with tentacles, and having 

 an upright oblique crest, or sail. The margins of the disk and crest 

 are often of a beautiful blue colour, and the canals of the disk become 

 deep blue as they approach the crest. The polypites may be blue, 

 purple, green, or brown. 



C. Medusidce. The structure and colouration of the true Medusae 

 are so like that of the medusiform larvae of the other Hydrozoa, that 

 they need not be particularly described. 



D. Lucernarida. Of this sub-class we need only cite the Lucer- 

 naria themselves ; which are pretty bell-shaped animals, having the 

 power of attaching themselves to seaweeds, etc., and also of swim- 

 ming freely about. Round the margin are eight tufts of tentacles, 

 opposite eight lobes, the membrane between the lobes being 

 festooned. In L. auricula, a British species, the membrane is colour- 

 less and transparent, the lobes bright red, or green, and the 

 tentacles blue. 



As a group the Hydrozoa display regional colouration in a very 

 perfect manner. 



IT. ACTINOZOA. 



It is not necessary to trace the colouration through all the 

 members of this group, but we will trace the variation of colour 

 through two species of anemonies, which have been admirably 

 studied by Dr. A. Andres.* The first column shows the general hue, 

 the second the tints of that hue which are sufficiently marked to 

 form varieties as cochineal red, chocolate, bright red, rufous, liver- 

 coloured, brown, olive, green and glaucous. The third column gives 

 the spotted varieties, from which it will be seen that the choco- 

 late, liver, and green coloured forms have each coloured varieties. 

 It will be seen that the range of colour is very great, passing from 

 pale pink, through yellowish-brown to blue-green. 



* Fauna mid Flora des Golfes von Neapel. Die Actinien. 1884. 



