CURIOSITIES OF STAR-FISH LIFE. 



3 6 7 



establish their hold upon it with their sucking-disks. This operation 

 may be witnessed by drawing a piece of sea-weed over a healthy 

 echinus in the water. 



The capability of the spines for co-ordinated action is highly re- 

 markable and interesting. Thus, for instance, if an urchin be taken 



Figs. 11 and 12. Righting and Ambulachal Movements of several Segments of Echinus. 



out of the water and placed upon a table, it is no longer able to use 

 its feet for walking, as the suckers can act only under water. Yet 

 the animal is able to progress slowly by means of its spines, which 

 are used to prop and push the globe-like shell along in some continu- 

 ous direction. If a lighted match be held in front of the moving ani- 

 mal, as soon as the echinus comes close enough to feel the heat, all the 

 spines begin to make the creature move away in the opposite direction. 

 There is an urchin-like form of echinoderm called spatangus, which 

 differs from the echinus in having shorter feet and longer spines. 

 When, therefore, a spatangus is inverted it is unable to right itself 



