THE BEHAVIOR OF THE SHORE-ANEMONE 309 



REACTIONS TO LIGHT 



The literature on the reactions of sea anemones to light indi- 

 cates that by far the greater bulk of these forms remain con- 

 tracted during the major portion of the day, expanding only 

 under the influence of darkness or during the hours of early 

 dawn and twilight. Hargitt (1907) has called attention to the 

 few observations which have been made on the sea anemones 

 in relation to light. According to the Hertwig brothers (1879), 

 Ouatrefages (1842) working on the species of Edwardsia found 

 that rays of light from a lamp concentrated upon the specimens 

 produced partial retraction. Haime (1854) observed in species 

 of Cerianthus that bright sunlight produced a contraction into 

 their tubes, expansion occurring when the light became less 

 intense. It was the experience of the Hertwigs (1879) that 

 from their observations on the deep-sea form, Cladactis costae 

 this species was more or less contracted during full daylight, 

 and expanded as the light became less intense. Jourdan (1889) 

 records a similar condition in a species of Peractis upon which he 

 experimented. . 



Hargitt (1907) found in Eloactis producta that: "It only 

 required a few observations to determine beyond doubt that 

 only in a light of low intensity, such as twilight, or in the aquar- 

 ium under the rather dim light of an incandescent lamp at 

 some distance, did the specimens protrude their oral portions 

 and tentacles and show any degree of activity." The same 

 worker found a like condition to hold in the case of Sagartia 

 leucolena. Metridhim he records as rather indifferent in its 

 responsiveness to changes, in light intensity. 



Jennings (1905) records Aiptasia annulata as "very sensitive 

 to light, expanding in darkness, but contracting after a few 

 seconds when exposed to strong light." 



Bohn (1907) discusses the light reactions of several species 

 of sea anemones and finds them very variable, dependent upon 

 many conditions. In some of them he -finds a persistence of an 

 impressed diurnal rhythm for three or four days after removal 

 from the sea. 



In specimens of Cribrina xanthogrammica the writer observed 

 that upon coming into the laboratory in the evening about seven 

 o'clock, the bulk of some fifty or more specimens kept in aquaria 

 were contracted. During the day they had been noted to be 



