THE GREEN CELLS OF CONVOLUTA ROSCOFFENSIS. 209 



tiou of it to colourless Convoluta^ the green animal has been 

 synthesised. 



In its free stage the infecting organism shows the essential 

 characters of the Chlamydomonadese ; its four equal flagella 

 point to its inclusion in the genus Carteria ; certain peculiari- 

 ties suggest that the assignment of the infecting organism to 

 this genus should be only provisional. The infecting organism 

 is capable of a saprophytic as well as of a holophytic mode of 

 life and occurs in both colourless and green forms. Its 

 saprophytic habit leads to its association with the egg- 

 capsules and constitutes a first physiological step toward its 

 association with the body of Convoluta. 



The green cells serve as an excretory system to the aniinnl. 



The relation between green cell and animal changes with 

 their development^ passing from a symbiotic relation to one in 

 which the animal is parasitic on the algal cells. 



The association leads to mai'ked changes of habit on the 

 part of the animal — e. g. to its ceasing from the ingestion of 

 food — and is best interpreted as an economically unsound 

 attempt on the part of both green cell and animal to solve 

 the " nitrogen problem." 



