68 Part second. 



POLYZOA or BRYOZOA. 



The name Poli/zoa, i. e. multiple animals, was given to this g-roiip 

 from the fact that they live in large colonies, like the corals. By the 

 German school they are always called Bryozoa or moss-animals, a name 

 which arose from the moss-like or coral-like growths which these col- 

 onies form. 



The g-racefnl net-like frill of Retepora (Fig. 116), or the branching- 

 stem of Mypiozoum (Fig. 117), may easily be mistaken for corals, to 

 which, however, they are 1)y no means allied. Careful observation has 

 shown that the little animals which form these growths, and live toge- 

 ther in colonies, are very different from, and more highly organized than, 

 the polypes of a coral. 



The Polyzoa are widely distributed in all seas, and present a won- 

 derful variety of form. A kind very common on the British coast and 

 well known to all visitors to the sea-side is the leaf-like growth of 

 Flustra, the sea-mat, the colour and texture of brownish white paper. 



CRABS, LOBSTERS, SHRIMPS, BARNACLES, etc 



(CRUSTACEA). 



These animals form a peculiar and very strictly defined group. 

 Contrasted Avith the quiet and dreamy lives of the brightly coloured 

 corals and the annelids, with the monotonous movements of the apathetic 

 fishes, and with the lazy moUusks and echinoderms, the active and often 

 comical movements of the difl^'erent kinds of Crabs are very attractive , 

 and we soon discover that the mental faculties of these creatures far 

 exceed those of most other marine animals. In making this statement 

 we have in mind chiefly the short-tailed Crabs and their allies, which 

 are found in tank Nr. 23 ; but as most people are better acquainted 

 with the long- tailed Lobster, Ave begin Avith the latter, and shall try to 

 explain the other kinds by comparison Avith the better-knoAvn animal. 



The Lobster, Homarus vulgaris (Fig. 163), is, on the whole, an 

 enlarged copy of the fresh-water crayfish; and visitors will easily recog- 

 nize, from examining the large specimens in the Aquariiim (tank Nr. 6), 

 what are the principal features of its organisation. The body is divided 

 into an anterior part, consisting of head and chest, which is really joint- 

 ed but covered on the upper sxirface by an unjointed shell {i^arnpace) ; 

 and a posterior part, composed of a number of rings forming the « tail » 

 of the Lobster, Avhicii terminates in a fin composed of broad, flat plates. 

 The anterior portion bears the stalked eyes and two pairs of antennfe 

 or feelers , one pair very long , the other short and forked. Behind 

 these, and on the under siirface is the mouth, furnished witli six pairs 

 of appendages or feet modified for purposes of mastication. Of these 

 first we have a pair of mandibles followed by two pairs of maxilla-,, 

 forming the « jaws » of the Lobster. Then there are three pairs of « foot- 

 jaws » or maxiHipedcs, tised by the animal to hold and turn about his 

 prey or food, Avhile the jaAvs proper are employed for biting and chew- 



