POLTZOA. 389 



fully complicated design, executed on a groundwork broad 

 as time, and whose scope and bearing are deep as 

 eternity." 1 



The Synaptida are characterised by a total absence of 

 ambulacra, the motions of the animals being assisted by 

 peculiar anchor-like processes of the calcareous grains 

 which project from the skin, and roughen the surface of 

 the animal. The spiculum represented at fig. 197 is ser- 

 rated on the convex edge, and the opposite extremity is re- 

 curved, and appears to be connected in some peculiar way 

 with the oval plate upon which it lies. It is a beautiful 

 object when made to depolarise light. 



Holothuridea, "Sea-cucumbers." In this order the 

 body acquires a worm-like form. The radiate structure is 

 in fact scarcely recognisable in these animals, except in 

 the arrangement of the tentacles which surround the 

 mouth. The body is always more or less elongated, with 

 the mouth at one end and the anal opening at the other ; 

 the calcareous deposit in the skin is reduced to scattered 

 granules ; and in one family the ambulacra are entirely 

 wanting. 



The Holoihurida inhabit the seas of most parts of the 

 world. Some of them are eaten even by European popu- 

 lations ; the Trepang (Holothurida edulis) is an article 

 of luxury amongst the Chinese. A few living specimens 

 were introduced into the tanks at the Zoological Gardens. 

 Unfortunately, they live only a few weeks when in a state 

 of captivity ; fig. 200 has been drawn from animals in Mr. 

 Lloyd's tanks. 



POLYZOA, or Bryozoa, placed by Dr. Johnston under 

 the head Ascidioida ; in the generality of works they are 

 named Bryozoa, and the individual, Bryozoon ; derived 

 from the Greek words j3pvoi>, sea-moss ; uor, animal. 

 (Fig. 201.) The distinction to be drawn between it and 

 the zoophytes previously described, consists in the poly- 

 pidom forming a living portion of the polype, while they 

 are unorganised ; and a few also of the zoophytes ex- 

 amined are devoid of cilia, whereas in the Bryozoon these 

 are most bountifully supplied. The play of the cilia is 

 most energetic, for the purpose of securing an abundant 



(1) Miller's Testimony of the Rocks. 



