66 Mr. F. Keeble and Dr. F. W. Gamble. Isolation of [Oct. 6, 



tropic in origin is shown by the fact that they may be produced without any 

 cells being killed. In Brunchhorst's experiments the electrolysis presumably 

 occurred in the superficial cells of the roots submerged in water, the tissues 

 being sufficiently impermeable superficially to the liberated acid and alkaline 

 ions to allow them to accumulate beyond the minimum for stimulation. 

 Although the curvature is usually sharp and strongly localised to the point 

 of application of the electrode, the discriminatory power of the root, as well 

 as the relation of the rates of growth Gn concave and convex sides to the 

 normal rate of growth, suffice to show that the response is a stimulatory one, 

 and is not due to the direct action of the products of electrolysis, retarding 

 growth on one side or accelerating it on the other. 



On the Isolation of the Infecting Organism (" Zoochlorella ") of 



Convoluta roscoffensis. 



By Feedekick Keeble, M.A., University College, Eeading, and F. W. Gamble, 

 D.Sc, University of Manchester. 



(Communicated by Sydney J. Hickson, F.E.S. Received October 6, 1905.) 



The present paper gives a preliminary account, (1) of experiments proving 

 that the green cells (" zoochlorellse ") of Convoluta roscoffensis result from 

 infection from without : (2) of the means whereby the infecting organism 

 may be cultivated outside the body of the animal : and (3) of the nature of 

 the infecting organism. 



1. Evidence for Infection. — In our former papers* we reached the con- 

 clusion that though direct proof of infection was lacking, the evidence 

 pointed most strongly to infection as the source of the green cells of 

 Convoluta. "We showed, moreover, that the difficulty in the way of obtaining 

 direct proof of the origin of these green cells is due to the fact that the mucil- 

 aginous capsules that invest the clutches of eggs laid by Convoluta are rarely, 

 if ever, sterile. Even when adults are washed repeatedly in sterilised sea- 

 water and caused to lay in sterilised surroundings, their egg-capsules become 

 covered in time with a varied flora of colourless and of green organisms. 



It is therefore necessary to isolate the young at the moment of hatching. 

 During the present summer we have done this in larger numbers than before 

 and maintained them in carefully filtered sea-water. Such young Convoluta 



* "The Bionomics of Convoluta roscoffensis," 'Boy. Soc. Proc.,' voL 72, p. 93, and 

 ' Quart. Journ. Micro. Sci.,' voL 47, p. 363, 1903. 



