86 



Papers from the Marine Biological Laboratory at Tortugas. 



5. Level of amputation has repeatedly been shown to affect considerably 

 the rate and nature of the regenerated organ. In these experiments all 

 arms were amputated at the same level, namely, at their respective bases. 



6. Temperature. By avoiding local heat and local drafts the temperature 

 was made uniform for the series. 



7. Preparation of the solutions. To avoid disturbing the "protective rela- 

 tion" of the salts and to avoid introducing any salt not normally present in 

 sea-water, the solutions were made as follows: The dilute solutions were 

 made by adding enough (rain) water to make solutions containing 95, 90, 

 85, 80, 75, 70, 65, 60, 55, 50, 45, and 40 per cent of sea-water. The rain- 

 water used in this series was tested by Dr. A. G. Mayer, who, upon the 

 basis of the chlorine content, calculated that it contained 0.001 part of sea- 

 water, an amount entirely negligible, as shown by these and other experi- 

 ments. The concentrated series was made by slow evaporation in the sun's 

 heat. In this manner, solutions containing 5, 11, 17, 25, 33, 42, and 53 per 

 cent more than the normal salts in sea-water were obtained. 



8. The number of arms amputated totaled 323. 



9. Three sets of measurements were recorded, 14, 24, and 30 days after 

 amputation. These measurements are given in table i. 



The data are plotted in figure i, in which the abscissas represent the 

 gradient solutions and the ordinates represent the average regeneration for 

 each solution. 



From table I and figure i , it will be observed that Cassiopea lived in 

 solutions in which the salt content varied from a lower limit of 40 to an upper 

 limit of 153 per cent. In the extreme solutions the medusae decreased in 

 size, ceased to pulsate, and the organs degenerated. This occurred in the 

 40 and later in the 45 per cent as well as the 153 per cent solutions. 



Within these limits the medusae lived and pulsated, but not all regener- 

 ated. No regeneration occurred in solutions containing 50 per cent or less 



