30 



LIFE BY THE SEASHORE. 



(Polychseta), are very numerous, and include many interest- 

 ing and beautiful forms. To them we shall return at 

 length. They are recognised by the 

 elongated segmented body, and the 

 ' p lateral tufts of bristles. 



The next group, somewhat iso- 

 lated in position, and not closely 

 related to the foregoing, is that of 

 the ECHINODERMS, or Prickly Skins, 

 including sea-urchins, starfishes, 

 brittle -stars, sea -lilies, and sea- 

 cucumbers; marine forms with limy 

 skeleton and radiate symmetry, al- 

 most always easy to recognise and 

 classify. They have a peculiar 

 " water vascular" system, which 

 in the common starfish, for example, 

 is connected with the delicate trans- 

 _g parent tube-feet, by means of which 

 the animal moves. 



The next great class is that of 

 the ARTHROPODS, or animals whose 

 bodies are made up of a series of 

 rings or segments, which are fur- 

 nished with hollow jointed feet. The 

 vast majority of the shore Arthro- 

 pods are CRUSTACEA, which take on 

 the shore rocks the place taken by 

 the Insects on land. The Crustacea 

 include crabs, lobsters, shrimps, sand- 

 hoppers, etc., animals with two pairs 

 of feelers on the head instead of one 

 FIG. 10 Fisherman's lob-worm pair as in Insects, with a har.l, limy 



Muft of bristles ;*; pa^aliV coat , and breathing by gills instead 



everted proboscis. A common of the air-tubes of Insects. Ihero 



are an enormous number of Crusta- 

 cea on the shore, where they occupy all zones from high- 

 tide mark to deep water. They are the great scavengers of 

 the sea, for many of them live on dead and putrefying 

 matter. In this respect also they resemble Insects, which 

 are the great carrion feeders of the land. 



