RATE OF REGENERATION IN CASSIOPEA 6 



In the course of my studies, which were taken up primarily to 

 reexamine the work of Stockard and Zeleny upon this point, I 

 discovered the marginal sense organs influence regeneration, inde- 

 pendent of their control of muscular activity. Such an influence 

 of the sense organs can be accounted for either on the ground that 

 metabolic activities, not expressed by muscular activity, are under 

 the control of the sense organs, or that a direct trophic influence 

 is exerted by the sense organs on the regenerating tissues. A 

 series of determinations with the 'biometer' of the rate of CO2 

 production by specimens imder different experimental conditions, 

 for which I am .indebted to Dr. S. Tashiro, shows that the first 

 of the two alternatives just mentioned offers a satisfactory ex- 

 planation of the observed facts. 



It is a pleasure to acknowledge ni}^ indebtedness to the author- 

 ities of the Carnegie Institution of Washington for putting at 

 my disposal the facilities of the laboratory at Dry Tortugas, 

 Florida, and especially to Dr. A. G. Mayer the director of the 

 laboratory for many helpful suggestions and constant interest 

 throughout the course of the work. 



TECHNIQUE 



As Mayer, Stockard and Zeleny have pointed out the disk of 

 Cassiopea wdll live for an indefinite period after the removal of 

 the oral arms and retain its full capacity for regeneration. These 

 nearly flat circular disks with their sixteen equally spaced sense 

 organs and with the ectodermal musculature entirely on the sub- 

 umbrella surface offer exceptionally favorable material for the 

 study of the phenomena of regeneration as they will withstand 

 practically any type of operation. 



The medusae can be procured in great numbers from the moat 

 at Fort Jefferson at Dry Tortugas, Florida, so that specimens of 

 any desired size c^n be selected for experimentation. In pre- 

 paring material for my experiments specimens of about 100 mm. 

 in diameter w^ere chosen, the oral arms and stomach removed as 

 soon as they were brought into the laboratory and the operations, 

 of whichever type, performed as soon as convenient, so that in 



