EXPERIMENTS ON ACTINIANS 



57 



required one hour. The animal remained in this 

 position for two days, and then crawled out of the 

 glass. 



In analysing the conditions that determine the 

 righting of the Cerianthus in this case, two circum- 





FIG. 14. CERIANTHUS REGAINING ITS NORMAL ORIENTATION. 



It was placed on the net horizontally, and within half an hour had regained its normal 

 vertical position, by pushing itself through the meshes of the net. 



stances must be taken into consideration, namely, 

 gravitation and the contact-stimuli. It can be easily 

 shown that gravitation alone is able to produce the 

 above-mentioned reaction of the Cerianthus. A wire 

 net, whose meshes are so fine that the body of a Ceri- 

 anthus can only be drawn through them by force, 

 is laid horizontally upon a glass standing in the 



