STAR-FISII AND SEA-URCHINS. 



311 



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 



Fig 61. 

 Figs. 59, 60, and 61 are righting movements of Echinns on a perpendicular suiface. 



feet which it employs shall be tliose which are as 

 far below the level of the feet in the row last em- 

 ployed as their length wdien fully protruded (i.e. 

 their power of touching the tank) renders possible. 

 The rotation of the orlobe thus becomes a double 



