Changes in concentration of sea water and their influence upon regeneration

Abstract

The regeneration under changed densities of sea water was observed under conditions that ensured the elimination or uniformity of associated factors such as size of medusæ, volume, surface and depth of solutions, extent of injury, level of amputation, temperature, crowding, aeration, etc. Furthermore, the dilute solutions were made with water containing a known quantity of sea salts, and the concentrated solutions were made by slow evaporation in the sun's heat, which corrected certain errors in previous experiments of this nature. The results were checked by repeated observations, plotted for intervals of 14, 24 and 30 days, after amputation of the arms of Cassiopea xamanacha.

These medusæ lived in solutions ranging from 40 to 153 per centum of the salts of sea water. They regenerated however in 50 to 133 per cent. solutions. The regeneration of normal arms and supernumerary arms was limited further to 75 to 105 per cent. solutions. Beyond these limits regeneration was atypic. Optimum regeneration occurred not in sea water but in sea water diluted 95 to 90 per cent. With increasing dilution the amount regenerated was diminished very slowly, with increasing concentration very rapidly. The subsequent examinations revealed the fact that in the sub-optimum solutions the arms regenerated absolutely and relatively faster than in any of the other solutions, correspondingly changing the character of the curve.

When the results were compared with those of Loeb it was found that both the hydroid Endendriurn of Woods Hole, Mass., as well as Cassiopea of Dry Tortugas, Fla., differed radically from the classic experiments of Loeb on Tubularia of Naples, in respect to the range of solutions in which animals lived or regenerated, the optimum solutions, the normality of the regenerated parts and the character of the curve.