208 F. KEEBLE AND F. W. GAMBLE. 



quenting the egg-capsules and also the surface slime of the 

 body of Convoluta is to be ascribed to its nitrogen require- 

 ments; this habit developed originally with no reference to 

 Convoluta (being shared with various Chhxmydomonadea; ; 

 e.g. Carteria subcordiformis, Wille n. sp. (1903)), was 

 nevertheless an essential preliminary to the association of 

 animal and green cell. 



(5) The association entails ultimately the death of the 

 green cell and of Convoluta; but whereas the former dies 

 without issue the latter first produces one or more batches 

 of eggs. 



(6) The consequences of the association are : To the green 

 cell hypertrophy, nuclear degeneration, premature senescence, 

 and death. To the animal : suppression of excretory system, 

 cessation of feeding, resignation of power of existence apart 

 from the green cells — i.e. obligate parasitism; adaptations 

 facilitating the photosynthetic activities of the green cell — 

 e. g. marked positive phototropism identical with that dis- 

 played by the infecting alga in its free state. 



Section VII. General Summary. 



Convoluta roscoffensis hatches out from its egg- 

 capsule as a colourless animal whose body contains neither 

 green cells nor antecedents of green cells. 



Infection takes place neither directly nor indirectly from 

 the body of the parent, but from the sea-water or from the 

 egg-capsules to which the infecting organism is cliemo- 

 tactically attracted and on which it habitually settles down 

 and develops. 



Experiment shows that the green cells of adult Convoluta 

 are incapable of life apart from the body of the animal ; 

 histological examination, proving that the development of the 

 green cell within the body is accompanied by degeneration of 

 its nucleus, supplies the explanation. 



The infecting organism has been isohited, and, by the addi- 



