THE BIONOMICS OP CONVOLUTA ROSCOFFENSIS. 875 



sea water^ and cutting off the light. The results of such 

 experiments show that the starch of the green cells — the 

 form in which the carbohydrate material is stored — disappears 

 with extreme slowness. During the first day oi' so the loss 

 of starch is too small to be estimated, and when experimenting 

 with adult Convoluta it is not until after eight days, in 

 minute green specimens not until after five days, that the 

 starch has entirely disappeared. The leaves of an ordinary 

 plant lose their starch when kept in the dark for a day or 

 two. The demands of the colourless parts are met by trans- 

 location of sugar. In Convoluta the demands of the 

 colourless tissues are extremely modest ; for it is not un- 

 reasonable to suppose that the needs of the green cells 

 themselves would account for the slow disappearance of 

 starch from tliem. The presence of brown masses of digested 

 green cells in such dark-kept adult Convoluta, and the 

 avidity Avith which they and the minute specimens take up 

 artificial substances, is an indication that the nutrition of the 

 animal is affected but slightly, if at all, by the absorption of 

 plastic material from the green cells. 



The conclusion, then, seems justifiable that the living green 

 cells purvey little, if au}^, nourishment to the animal at any 

 stage of its development, and that the association between 

 the green cells and Convoluta is best represented as being 

 a form of parasitism. During the earlier stages of the life 

 of Convoluta it is the assimilating tissue which is parasitic 

 upon the animal; during the later ones it is the animal which 

 is parasitic upon the assimilating tissue. 



3. Photosynthesis. 



It is doubtful how far the starch formed by the green cells 

 of Convoluta may be translocated from them and used by 

 the animal cells; but there is no doubt that starch is manu- 

 factured, and that in considerable quantities. Haberlandt, in 

 experimenting with animals sent from Roscoff to Gratz, notes 

 that the amount of starch contained in the green cells is but 



