Part second. 



POLYZOA or BRYOZOA. 



The name Polyzoa , i. e. multiple animals, was given to this group 

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

 man 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 graceful net-like frill of Retepora (Fig. 116), or the branching 

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

 which, however, they are by no means allied. Careful observation has 

 shown that the little animals which from these growths, and live together 

 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 Flu- 

 Stra, 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 denned group, Con- 

 trasted with the quiet and dreamy lives of the brightly coloured corals 

 and the annelids, whith the monotonous movements of the apathetic fishes. 

 and with the lazy mollusks and echinoderms , the active and often co- 

 mical movements of the different kinds of Crabs are very attractive, and 

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

 those of most marine animals. In making this statement w r e 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, we begin with the latter, and shall try to explain the other 

 kinds by comparison with the better-known animal. 



The Lobster. Homarus vulgaris (Fig. 162), 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 Aquarium (tank Nr. 6) 7 

 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 surface by an unjointed shell (carapace)', 

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

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

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

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

 and on the under surface is the mouth , furnished with six pairs of ap- 

 pendages or feet modified for purposes of mastication. Of these first we 

 have a pair of mandibles followed by two pairs of maxillae, forming the 

 jaws of the Lobster. Then there are three pairs of foot-jaws or 

 inaxillipedes . used by the animal to hold and turn about his prey or 



