DIFFUSED CIRCULATION. 233 



move in a circuit, even when not confined within 

 vessels or narrow channels ; for this movement of 

 rotation, or cyclosis, as it has been termed,* what- 

 ever may be its cause, appears always to have a 

 definite direction. The current returns into 

 itself, and continues without intermission, in a 

 manner much resembling the rotatory movements 

 occasionally produced in fluids by electro-mag- 

 netism, f 



Movements, very similar in their appearance 

 and character to those of vegetable cyclosis, 

 have been recently discovered in a great 

 number of polypiferous Zoophytes, by Mr. 

 Lister, who has communicated his observa- 

 tions in a paper which was lately read to the 

 Royal Society, and of which the following are 

 the principal results. In a specimen of the 

 Tuhularia indivisa, when magnified one hundred 

 times, a current of particles was seen within the 

 tubular stem of the polype, strikingly resem- 

 bling, in the steadiness and continuity of its 

 stream, the vegetable circulation in the Chara. 

 Its general course was parallel to the slightly 

 spiral lines of irregular spots on the surface of 

 the tube, ascending on the one side, and de- 



* See pages 49 and 50 of this volume. 



+ So great is this resemblance, that it has led several physiolo- 

 gists to ascribe these movements to the agency of electricity ; but 

 there does not, as yet, appear to be any substantial foundation for 

 this hypothesis. 



