CHAPTER IV 



THE ORIGIN AND NATURE OF THE GREEN CELLS 

 OF CONVOLUTA ROSCOFFENSIS. 



GREEN, yellow or brown cells, resembling in a 

 general way those contained in the bodies of C. ros- 

 coffensis and C. paradoxa, are found in many different 

 kinds of animals belonging to the lower groups of the 

 animal kingdom. 



Such cells are known to exist in representatives 

 of every division of the free-living Protozoa the 

 lowest group of animals. They occur in certain 

 sponges, in many sea-anemones and in various 

 species of coral-forming animals. In higher groups, 

 they are rare though they are known to occur in 

 isolated cases, for example, in Zoobothrium, a 

 member of the Polyzoa, in Elysia (a Mollusc), and 

 in Echinocardium (an Echinoderm). 



The best known example of an animal containing 

 green alga-like cells is the common, freshwater hydra, 

 Hydra viridis. 



In certain of the animals which are characterised 

 by the possession of coloured cells, these peculiar 



