272 JELLY-FISH, STARFISH, AND SEA-URCHINS. 



The Ecliiniis crawls in the same way as the 

 common Star-fish; but besides its long suckers it 

 also uses its spines, wdiich by their co-ordinated 

 action push tlie animal along. The suckers, more- 

 over, in being protruded from all sides of a globe 

 instead of from the under side of a flat oi'ganism, 

 are of much more use as feelers than they are in the 

 Star-fish. Therefore, wdiile advancing, the feet 

 facing the direction of advance are always kept 

 extended to their fullest length, in order to feel for 

 any object which the animal may possibly be 

 approaching. When a perpendicular surface is 

 reached, the Echinus may either ascend it or not, as 

 in the case of the Star-fish. While walking, the 

 animal keeps pretty persistently in one direction 

 of advance. If it be partly rotated by the hand, 

 it does not continue in the same direction, but 

 continues its own movements as before ; so that, 

 for instance, if it is turned half round, it will 

 proceed in a direction opposite to that in which 

 it had previously been going. When at rest, some 

 of the feet are used as anchors, and others protruded 

 as feelers. 



Regarded from the standpoint of the evolutionist, 

 we have here an interesting series of gradations. 

 At one end of the series we have the Echinus with 

 its rays all united in a box-like rigid shell. At 

 the other end of the series we have the Brittle-stars 

 and Comatuhie with their highly muscular and 



animals, nevertheless in this particular case and in virtue 

 of special modilication, a Star-fish should have adopted the plan 

 or mechanism of a Jelly-fish. 



