2/8 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 



tliev assist in increasing^ the tilt ; then the next feet 

 in the series lay hold, and so on, till the globe 



Fig. 50. 



slowly but steadily rises upon its equator (Fig. 51). 

 The difficulty of raising such a heavy mass into 



Fig. 51. 



this position by means of the slender motive power 



