70 



Papers from the Marine Biological Laboratory at Tortugas. 



Table lo shows the decHne in weight of 6 normal medusae of Cassiopea 

 xamachana starved 26 days in filtered sea-water in the dark at temperatures 

 ranging from 27,3° to 30.1° C, from June 18 to July 14, 191 1, at Tortugas, 

 Florida.^ The medusae were placed in a 6-liter glass aquarium, the water 

 being changed once in each 24 hours. The temperature conditions were 

 similar to those maintained for the medusae whose rates of decline are 

 shown in table 4. 



Table 10. 



> According to the formula y = 85.6(1 — 0.075)*- 



Remarks. — ^These 6 medusae were captured in the moat of Fort Jefferson, Tortugas, on June 16 and 

 weighed for the first time on June 18, 1911. The smallest was about 25 mm. wide on June 18. On June 22 

 the smallest was only 8.5 mm. wide, and by June 25 and 26 the medusae had begun to macerate. 



909 



6 medusae starved 26 

 days in the dark 



Diagram illustrating Table 10. 



1 For the first 14 days the medusae remained in complete darkness, not being exposed for an instant to 

 the light. On the fourteenth day they were observed in diffuse light, and it appeared that they were all blue- 

 translucent, not greenish gray, as are the normal medusae. The algal cells were then greatly reduced in number. 

 The medusae were then replaced in the dark as soon as possible, and remained in darkness until the end of the 

 experiment, excepting that from the fourteenth to the twenty-sixth day they were weighed in the diffuse light 

 of the laboratory but were replaced in the dark room immediately after each weighing. 



