90 



Papers from the Marine Biological Laboratory at Tortugas. 



Whether we consider only the regeneration of the supernumerary arms 

 or of single arms, or normal as opposed to abnormal regeneration, or the 

 variation in growth at different intervals, or all of these combined, it is 

 clear that the maximum regeneration in Cassiopea occurs in sea-water di- 

 luted to 95, 90, and 85 per cent. 



There are three sets of records complete enough to permit comparison, 

 namely, Loeb's work on Tubularia,^ Goldfarb on Eudendrium,'^ and the 

 present contribution on Cassiopea. 



Loeb's data are based upon the regeneration of 65 pieces of Tubularia 

 stems over a period of 8 days. The work was done at Serino where the sea- 

 water is estimated on the basis of Forchhammer's calculation to contain 

 3.8 per cent salts or more correctly 38.364 per kilogram. Loeb used 10 

 grades of solutions and plotted his results as shown in figure 3. 



160 140 130 120 110 100 ,90 80 70 /60 ,60 40 



The 323 Cassiopea arms observed at 14, 24, and 30 day intervals in sea- 

 water whose salinity, though not definitely known, is calculated^ to be 3.549 

 per cent. The medusae were placed in 20 graded solutions. The results 

 differ from Loeb's in at least four respects: 



1. The salinity limits are different, i. e., Tubularia regenerated in more 

 dilute solutions than Cassiopea, though the extreme concentration is prob- 

 ably the same for both. 



2. Maximum regeneration occurs at different salinities, 65 per cent sea- 

 water for Tubularia, 95 per cent for Cassiopea. 



3. There is a greater range of supernormal regeneration in Tubularia 

 i. e., 100 to 50 per cent salinity, while the range for Cassiopea is limited to 

 15 per cent, i. e., from norm to 85. 



4. The character of the curves is reversed. For Tubularia there is a 

 graded increased regeneration with increasing dilution from 133 to 65 per 

 cent; beyond this limit there is a sudden drop to complete inhibition in 40 

 per cent. The Cassiopea curve on the other hand rises rapidly to 95 per 

 cent, beyond which there is a very gradual decrease (fig. 3). 



The third set of observations were those on the compound hydroid 

 Eudendrium ramosum. The results of one series, based on 953 stems, are 

 plotted in figure 4, and when compared with Tubularia and Cassiopea show 

 the following: 



' Loeb, J. Organization and growth. Wurtzburg. 1891. 



' Goldfarb, A. J. Factors in the regeneration of a compound hydroid, Eudendrium ramosum. Jour. Exper. 

 Zool., vol. 4, p. 43. 1907. 



» Clarke, F. W. The data of geochemistry. Bull. 491. U. S. Geol. Survey. 191 r. 



