Regeneration 



171 



regenerate the more quickly the nearer they are to the 

 oral pole. If this were correct, and we cut a long piece 

 from the stem of a Tuhularia and bisect the piece, the 

 oral pole of the anterior half should regenerate more 

 quickly than the oral pole of the posterior half. Accord- 

 ing to the writer's observations on a Tubularian {T. 

 crocea) growing in the estuaries 

 near Oakland, California, both oral 

 ends regenerate equally fast in such 

 cases. 



4. The phenomena of regenera- 

 tion in Cerianihus membranaceus, 

 a sea anemone, can be easily under- 

 stood from the experiments on 

 Tubularians, if we imagine the 

 body wall of Cerianihus to consist 

 of a series of longitudinal elements 

 running parallel to the axis of sym- 

 metry of the animal from the tenta- 

 cles to the foot. The number of these elements may 

 be supposed to correspond to the number of tentacles 

 in the outer row of the normal animal. Each such ele- 

 ment behaves like a Tubularian, with this difference, 

 however, that the elements in Cerianihus are more 

 strongly polarized than in Tuhularia, and that each 

 one is able to form a tentacle at its oral pole only. 

 This fact can be nicely illustrated in the following way : 

 if a square or oblong piece (abed, Fig. 24) be cut from 



Fig. 24 



