THE ECHINODERMATA 123 



for a creature armed with prickles. The Greek 

 word echinos also means a hedgehog, so that the 

 long name given to the group means simply 

 hedgehog-skinned. The prickles attain their 

 maximum in the Sea-Urchin, but they are well 

 represented in the Star-fish, while in the Sea- 

 cucumber the general tendency to " prickliness " 

 is much reduced, and represented only by 

 "spicules" (needles) of shelly stuff underneath 

 the skin of the animal. 



The largest and the most beautiful of the Sea- 

 Urchins of the English coast is known as the Pur- 

 ple-tipped Sea-Urchin, on account of the beautiful 

 colour of the spines. It lives on rocky coasts, 

 and during very low tides may be seen at home, 

 although it usually takes care not to stray above 

 the water-line. It is a shelly ball with a flat 

 base; its surface is covered with long spines. 

 Its mouth, which is in the centre of the base, 

 shows five wicked-looking teeth peeping out. 

 The shell is pierced by what look like hundreds 

 of minute pin-holes, arranged in a complicated 

 pattern ; these are the holes through which it 

 pokes its feet, which greatly resemble those of a 

 Star-fish, being white suckers with a disc at the 

 end. When thrown out to their full length they 

 are, however, much longer than those of the Star- 

 fish, for they are naturally obliged to be thrown 

 out to a distance longer than the length of the 

 animal's own prickles. When moored by all its 

 feet, extended from all sides of the shelly ball, 

 the animal presents a curious and pretty sight. 

 Large specimens are almost as big as a child's 

 head, but smaller ones are more common. There 

 is a considerable range of variation in colour ; 

 not only are various shades of purple found, but 



