VITALITY OF ACTINIA BERMUDENSIS 361 



They conclude, therefore, that C. roscoffensis has not lost its 

 power of independent nutrition, and that it obtains but little food 

 from the green cells. They find, in addition, that the green cells — 

 Zoochlorellae^ — are not developed by the animal itself, but are 

 organisms which infect the animal from without, entering the 

 host usually as colorless leucoplasts, which only subsequently 

 develop their green pigment. As to the physiological relation of 

 the algae to the worm, Gamble and Keeble conclude that it 

 changes with development, passing from one of true symbiosis, 

 in the early stages of development, to one in which the turhellarian 

 is 'parasitic upon the algal cells. The evidence for this last conclu- 

 sion was threefold: 1) in the first place, during starvation Con- 

 voluta digests its green cells; 2) the Zoochlorellae never reproduce 

 after infecting the worpi; 3) the association of the green algae 

 with the turbellarian is followed by a degeneration of the worm's 

 excretory system — the algae utilizing the worm's nitrogenous 

 waste, thus functioning as an excretory apparatus for the animal. 

 It must be emphasized, therefore, that the association between the 

 algal cells and C. roscoffensis is not one of symbiosis, but a rela- 

 tion of obligate parasitism. 



Let us return now to the condition in Actinia bermudensis. 



The results for A. bermudensis recorded in the first part of 

 the present paper (table 1, p. 358) seem to agree in many ways with 

 those of Gamble and Keeble for C. roscoffensis. In the first 

 place, there is no evidence that the products of photosynthesis 

 from the Zooxanthellae assist in the nutrition of the actinian. 

 Furthermore, it is probable, from certain observations of Brandt 

 ('83) and from those which the writer has made upon Condylac- 

 tis passiflora, that during starvation the anemone feeds upon the 

 'yellow cells' rather than upon their photosynthetic products. 

 It seems a safe deduction, also, that, as in Convoluta, the ' yellow 



^ It is largely a matter of personal judgment whether one considers Zoo- 

 chlorellae and Zooxanthellae as Algae or Protozoa. Minchin ('12) has adopted 

 the arbitrary method of considering all Zoochlorellae — forms having green pig- 

 ment — as Algae, while the Zooxanthellae — with yellow pigment — he classifies 

 as Protozoa. This classification, being convenient, has been adopted in the 

 present paper. 



