STAR-FISH AND SEA-URCHINS. alt 
direction of lateral rotation, and so the process pro- 
ceeds from row to row; but the globe does not 
merely roll along in a, horizontal direction, or at the 
same level in the water, for each new row that 
comes into action takes care, so to speak, that the 
? 
MAN} 
X 
INN 
INN 
AGG 
MG 
Fig. 61. 
Figs. 59, 60, and 61 are righting movements of Echinus on a perpendicular surface. 
feet which it employs shall be those which are as 
far below the level of the feet in the row last em- 
ployed as their length when fully protruded (ve. 
their power of touching the tank) renders possible. 
The rotation of the globe thus becomes a double 
