DIVISION OR TYPE V.: SPINY-SKINNED ANIMALS 

 (ECHINODERMATA). 



Radially symmetrical, usually five-rayed animals, with the , integument 

 hardened by calcareous deposits, usually raised above the surface in the 

 form of spines, and provided with a water-vascular system, which is 

 continued into the organs of locomotion (sucking- feet). Of marine habitat. 



CLASS I. : STAR-FISHES (ASTEROIDEA). 



The Common Star-Fish (Asterias rubens). 

 (Diameter usually from 4 to 6 inches.) 



A. Distribution. 



The star-fish is common on all European coasts excepting those of the 

 Mediterranean. (See illustration, p. 462.) People living inland regard 

 this animal with special interest — not only on account of its variable 



B. Colour, 



red, yellow, brown, to almost black, but principally on account of its 

 utterly unusual 



C. Shape, 



which is that of a five-rayed star (name). The lobes which radiate from 

 the central, disc-shaped body are called " rays " or " arms." All the 

 animals hitherto considered were bilaterally symmetrical ; i.e., their 

 body was divisible by one section into two similar halves, and in them 

 we were able to distinguish a right and left side and a front and back. 

 The body of a star-fish, on the other hand, consists of five similar parts ; 

 for if we draw imaginary lines from the centre of the disc to the angles 

 between the radii, we obtain five such similar segments. (The number 

 five is very frequently repeated among the eehinoderms, as we shall see 



