354 JOHN F. FULTON, JR. 



a slide.2 When a fresh smear of the gastrovascular fluid is ob- 

 served, the Zooxanthellae are usually in a state of active vibra- 

 tion. Their flagella, though not visible in the living condition, 

 may be observed after adding a drop of a mixture of acetic and os- 

 mic acids. The organism contains a yellow pigment, hence the 

 name 'yellow cells' (Geddes, '82), which functions photosyn- 

 thetically, and it is therefore of interest to learn whether or not 

 the Zooxanthellae present in A. bermudensis are truly symbiotic,^ 

 and whether they are responsible in any way for the great vitality 

 which the anemone possesses. In an effort to answer these ques- 

 tions, a series of simple experiments was made. 



These consisted in subjecting specimens of the anemone to 

 varied environmental conditions, and using for controls specimens 

 kept in the dark, but otherwise under the same enviromental con- 

 ditions. Since the Zooxanthellae could be of functional value 

 to the anemone only through action of sunlight, the possible aid 

 derivable from their presence would be cut off so long as the 

 anemone was kept in darkness. The individual anemones kept 

 in sunhght ought, therefore, to exhibit greater vitahty than those 

 kept in darkness, if the Zooxanthellae contribute through their 

 photosynthesis to the nutrition of the anemones. 



Experiment 1 — Sea-water. Each of the anemones^ of the 

 first group was placed in a bottle containing 100 cc. of unsteri- 

 lized sea-water on July 14th, sealed, and allowed to remain until 

 dead.^ On July 19th all of the actinians appeared to be aUve. 



2 Zooxanthellae are common in most actinians. The writer has noted them 

 in Condylactis passiflora D. &. M. (in which they are responsible for the color 

 of the tentacles), Aiptasia tagetes D. & M., and Epicystis osculifera Verrill; 

 Gary ('11) has reported them also in: Aiptasia pallida Ag., A. annulata Andres, 

 and Cylista leucolena Ag. ; they have also been described by Heilprin ('89) for 

 many species of Zoanthidae. In the course of the present study, Zooxanthellae 

 were also noted in several species of gorgonians, particularly in Plexaura flexuosa 

 Lamx. In the rose coral, Isophyllia (dipsacea and fragilis), is found a holophytic 

 organism which is probably closely allied to Zooxanthella. 



3 Winter ('07) has shown that Zooxanthellae are symbiotic in Peneroplis (a 

 foraminiferon). 



^ Three animals were used for each experiment. 



^ The only way by which it could be determined with absolute certainty 

 whether or not an animal was dead was to remove it from the air-tight bottle 



