THE. BIONOMICS OF CONVOLUTA EOSCOFIENSIS. 383 



The suggestion made by Georgevitcli is based on the 

 result of hatching Convoluta in filtered sea water as con- 

 trasted with rearing it in water containing the parent forms. 

 In the first case the young hatch and die within two days, 

 during which time they remain colourless. In the second 

 they survive and become rapidly green. Georgevitch con- 

 cluded that the just-hatched young became infected by green 

 cells from the water containing the parents. 



In the following section we show that there is no such 

 hereditary transmission of green cells as Haberlandt postu- 

 lated, nor is there an infection of Convoluta by green cells, 

 as Georgevitch concluded. ^.r 



Since the structure of the green cells does not allow a 

 precise statement of their animal or vegetable nature, proof 

 must be sought in their development. It might be thought 

 no difficult matter to determine this point by rearing the 

 eggs in sterilised water. The sequel, however, makes it 

 clear that no experiment made with a view of settling the 

 nature of the green cells can be considered valid if the egg- 

 capsule is introduced — a conclusion which we have arrived at 

 only after many laborious experiments. In fact, to obtain 

 eggs or larvfe and to place them in experimental vessels in 

 such a way as to satisfy the demands of the most rigorous 

 criticism that no infecting organism is thereby introduced, is 

 an exceptionally hard task. Yet, unless this difficulty is 

 overcome, the problem of the nature of the green cells 

 cannot be finally decided. 



3. The Origin of the Green Cells. 



At the time of hatching, Convoluta roscoffensis has 

 no green cells, no colourless cells that can be interpreted 

 as a stage in the development of such green cells, and no 

 leucoplasts. 



We have satisfied ourselves by repeated observation that 

 no green cells are present at hatching. That no colourless 

 antecedents occur in the just-hatched animal, follows both 



