THE GREEN CELLS OP CONVOLUTA ROSCOFFENSIS. 181 



It only remained, therefore, to apply the inoculation test — 

 that is, to submit colourless, uninfected animals reared in 

 filtered water to the chance of infection by these flagellated 

 cells. A batch of such animals was divided accordingly into 

 three groups. One, serving as a control, was maintained in 

 filtered water ; another, also a control, was placed in unfiltered 

 sea-water in order that its capacity for infection might be 

 tested; the third was put into filtered sea-water to which 

 numbers of the flagellated organism had been added. The 

 result proved conclusively that these flagellated cells are a 

 stage in the life-history of the infecting organism. Group 1 

 in filtered sea-water remained, uninfected ; Group 2 in 

 unfiltered sea-water showed the susceptibility of the animals 

 to infection: they became green in the course of three days; 

 Group 3, exposed to infection by the flagellated cells, were 

 observed to ingest these cells, to tolerate their active division, 

 and to become in consequence normal green Convolutas. 

 Subsequently, when we had perfected our procedure so as to 

 be able to obtain fairly constant supplies of the flagellated 

 cells, we repeated the experiment frequently, and in all cases 

 with the same result. Thus Convoluta has been synthesised 

 from its elements the colourless animal and the green, 

 flagellated cell. 



Summary of Section III. 



(1) We have isolated and cultivated outside the body of 

 Convoluta its infecting organism. 



(2) It is not from the green cells of the body of Convoluta 

 that the infecting organism may be isolated, but it may be 

 obtained readily from the remnants of the egg-capsules. 



(3) The infecting organism which occurs sporadically on 

 the egg-capsules is derived, not from the green cells of the 

 body of the parent, but from free cells frequenting the surface 

 of the body at the time of egg-laying. 



(4) If to filtered sea-water containing colourless Convoluta 

 the infecting alga is added the synthesis of the green animal 

 results. 



