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,* 

 whatever 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 move- 

 ments occasionally produced in fluids by electro- 

 magnetism, t 



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 observations 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 Tubularia indivisa, when 

 magnified one hundred times, a current of 

 particles was seen within the tubular stem of the 

 polype, strikingly resembling, in the steadiness 

 and continuity of its stream, the vegetable cir- 

 culation 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 descending on the other ; 



* See pages 49 and 50 of this volume. 



f So great is this resemblance, that it has led several physi- 

 ologists to ascribe these movements to the agency of electricity ; 

 but there does not, as yet, appear to be any substantial founda- 

 tion for this hypothesis. 



