326 NATURAL HISTORY OF 



Genus Ceistatella^ Cuvier. {Crista, a crest.) 



Ccenoecium sacciform, hyaline, with a common flat- 

 tened disc, adapted for locomotion ; orifices placed on 

 the surface opposite to the disc, and arranged in several 

 concentric marginal series. Statohlasts orbicular, with 

 an annulus and marginal spines. — Allman. 



1. C. MUCEDO, Cuvier. Plate XXIV. fig. 1. 



C. vagans [LamTc., Jjamx., Schiveigger, Goldfuss, De 

 Bl.), C. mirabilis (Dalyell), C. moissisure {Gervais), 

 Alcyonella secundus evolutionis gradus {Ras])ail). 



Hab. : Lakes and ponds. 



This is the only polyzoon which is locomotive. It 

 creeps along by its flattened disc over the stems and 

 leaves of aquatic plants. The entire colony is oval, 

 convex above, and flattened into the locomotive disc 

 below. The orifices through which the polypides 

 emerge are ranged in three concentric rows a little 

 above and around the margin of the upper surface, 

 leaving the central portion of the convexity without 

 openings. 



The statoblasts are veiy pretty objects, and are 

 about -Jyj inch in diameter. They are orbicular in 

 shape, reddish-brown in the centre, surrounded by an 

 annulus which is yellowish in colour, and armed with 

 spines projecting beyond the annulus and terminating 

 in curved hooks. (Plate XXIV. fig. 2.) 



FAMILY II. PLUMATELLIDiE. 



Ccenoecium rooted. 



Genus TjOFROfvs, Dumortier. (\o'(^o9, a crest ; 

 TToi)?, a foot.) 



Ccenoecium sacciform, hyaline, with a disc which 



