92 



Papers from the Marine Biological Laboratory at Tortugas. 



Table 6. 



In these three organisms the increasing dilution of sea-water, with the 

 consequent intake of water into the organism, makes for a more rapid and 

 greater growth. Beyond an optimum dilution, any further dilution retards 

 and ultimately inhibits regeneration. Concentration of sea-water, in all 

 cases, makes for an expulsion of water from the organism, with a concomitant 

 retardation, decreased regeneration, and finally no regeneration whatsoever. 

 Beyond these fundamental similarities, there is little or no agreement. 



Though there appears to be little or no similarity in the behavior of 

 these three organisms, on further examination it becomes quite clear that 

 Eudendrium and Cassiopea are in essential agreement, both differing in a 

 striking manner from Loeb's results on Tubularia. 



Eudendrium and Cassiopea agree in the following respects: (i) maximum 

 regeneration occurs in solutions that are hypotonic in a relatively small 

 degree, i. e., 95 and 85 per cent respectively; (2) regeneration in sea-water 

 is equaled or exceeded in a narrow range of hypotonic solutions, i. e., 100 

 to 85 and 80 per cent, respectively; (3) at any interval after amputation, the 

 graphs show a sharp decline in the amount regenerated in increasingly 

 hypertonic solutions ; a maximum regeneration of not more than 60 per cent 

 beyond the norm, i. e., 60 per cent in Cassiopea, 35 per cent in Eudendrium; 

 a gradual followed by a more rapid drop in the curve, in solutions more 

 hypotonic than these optimum solutions. 



It is in these very points that both these curves differ from Loeb's 

 work on Tubularia, as follows: The maximum regeneration occurred in a 

 markedly greater hypotonic solution, i. e., 65 per cent; regeneration in sea- 

 water is equaled or exceeded in a considerably wider range of diluted so- 

 lutions, i. e., 100 to 50 per cent solutions inclusive; the curve is completely 

 reversed, the gradual increment and the sharp decline appearing on sides 

 opposite to that in either Eudendrium or Cassiopea; the mode is nearer the 

 extreme dilution; and the maximum regeneration is far greater (120 per 

 cent) than in either of the other two organisms. 



It is estimated that the maximum salinity of the sea-water at Woods 

 Hole, Massachusetts, is 3.29,^ for the Dry Tortugas 3.54 per cent.^ It 

 might be urged that a definite relation obtains between the density of the 

 sea and the regeneration of the contained organism, subjected to a graded 



* Bulletin of Bureau of Fisheries, vol. 31. 1911. 



» Clarke, F. W. The Data of Geochemistry. Bull. 491, U. S. Geol. Survey. 1911. 



