THE BIONOMICS OF CONVOLUTA BOSCOFFENSIS. 309 



set free from the grceu cells, and possibly also by osmotic 

 translocation of a soluble carboliydrate from the green cells 

 to the surrounding- tissues. 



The special adaptations of Convoluta i-oscoffensis have 

 been regarded by previous writers as contrivances for ensuring 

 the continued assimilation by the green cells and the nutrition 

 of the animal. 



Its body has become elongated and flattened, exposing a 

 great extent of surface to the light. Its station is high up 

 on the beach, where the greatest amount of light and yet a 

 sufficiency of moisture may be obtained. It forms vast inert 

 patent colonies protected from attack by the nauseous alka- 

 loid ([)robably trimethylamiu) which, as Geddes has shown, 

 Convoluta excretes. In these several ways, Convoluta 

 stands in marked contrast to its retiring submerged troglodyte 

 allies ; and it has been assumed that the special mode of life 

 of Convoluta and its peculiar tropisms adapt it for its 

 special holophytic mode of nutrition. 



That its station high up on the beach ensures to Con- 

 voluta roscoffensis a prolonged daily light exposure is 

 clear enough. That its flattened form and peculiar tropisms 

 favour photosynthesis is also certain. Nevertheless the view 

 held by previous authors that Convoluta is holophytic in 

 its mode of nutrition is either an inference from these facts 

 of adaptation, or is based on negative evidence, viz. the 

 absence of food in the bodies of the animal. We show that 

 the evidence is unsound, and that we must interpret the 

 relation between the "green cells" and the animal in a 

 different way. 



Before recording our own observations we may remark 

 that Convoluta is not the only animal in which observers 

 have failed to demonstrate the presence of food, and it is 

 noticeable that the presence of yellow or green cells is 

 frequently correlated with this abstemious habit. For 

 example, no food has been found in the tissues of certain 

 adult Radiolaria (Brandt, 1882), Ciliata ( Entz, 1881-2), 

 Hydrocorallines (Hickson, 1889), Madreporaria (Hicksou, 



VOL. 47, PART 3. NKW SERIES. A A 



