362 . JOHN F. FULTON, JR. 



cells ' of A. bermudensis facilitate excretion by utilizing the nitro- 

 genous waste, as well as the carbon dioxide, from the animal. 

 In other words, the condition of association would seem to be one 

 in which the actinian is parasitic upon the Zooxanthellae which it 

 contains. 



Arndt ('13) has recently published certain results which are 

 not entirely in agreement with my own conclusions. He has 

 shown that the fat globules in the entoderm and ectoderm of the 

 anemone Heliatis bellis appear to be identical with the lipoid 

 substances in the Zooxanthellae, and concludes that the cells 

 must function in the nutrition of the actinian. He believes that 

 the fat globules are photosynthetic products, and holds, therefore, 

 that the association must be one of true symbiosis. This conclu- 

 sion does not seem to be entirely justifiable, inasmuch as the evi- 

 dence for the identity of the fat in the animal tissue on the one 

 hand and that of the Zooxanthellae on the other is by no means 

 conclusive. 



CONCLUSIONS 



Actinia bermudensis possesses a remarkable resistance to un- 

 favorable environmental conditions (table 1). Sealed in 100 

 cc. of sea- water it will live for six days; in O2 for seven days, and 

 in 100 cc. of air (sealed by water) for more than eleven days. 



The holophytic organisms (Zooxanthellae) do not materially 

 assist the actinian in resisting unfavorable conditions, for when 

 placed in the dark the animal is as well able to resist such condi- 

 tions as it is in the light. 



As with the green cells in Convoluta roscoffensis, so well de- 

 scribed by Keeble and Gamble, the association between the Zoo- 

 xanthellae and A. bermudensis is probably one of obligate para- 

 sitism — the actinian being parasitic upon the Zooxanthellae. 



Harvard College, Cambridge, Massachusetts. 



