DEPARTMENT OF MARINE BIOLOGY. 145 



Preliminary Report upon Investigations, by A. J. Goldfarb. 



SALINITY CHANGES AND THEIR EFFECTS UPON THE REGENERATION OF 



CASSIOPEA XAMACHANA. 



The amputated oral arms of this large medusa served as a basis for the 

 determination of the influence of changes of salinity of sea-water upon re- 

 generation. With the containing vessels, quantity of solution, temperature, 

 evaporation, extent of injury, size of medusa, and other factors uniform, 

 the variable factors were reduced to two, namely, density of sea-water and 

 amount regenerated. The use of distilled water for purposes of dilution 

 and of sea-water concentrated by slow evaporation corrected certain errors 

 in previous experiments of this nature. 



There were 323 oral arms amputated at approximately the same level. 

 After a month's interval the final measurements gave the following: Maxi- 

 mum regeneration did not occur in normal sea-water, but in water diluted 

 5 to 10 per cent. This is in accord with the author's previous work on 

 hydroids. A more limited regeneration occurred both in normal sea-water 

 and in dilutions of 10 to 15 per cent. In these three solutions regeneration 

 was practically the same. With increasing dilution the amount regenerated 

 decreased until a density of 55 was reached, beyond which no regeneration 

 whatsoever occurred. 



In contradistinction to the wide range of dilutions in which considerable 

 regeneration occurred, even small concentrations appeared to be very in- 

 jurious. In a density of 1.05 the amount regenerated was less than that in 

 a 0.55 solution. Very little regeneration occurred in a density of 1.11 and 

 1. 17, falling off rapidly in densities of 1.25 and 1.33, beyond which regenera- 

 tion ceased altogether. In the latter solutions, furthermore, regeneration 

 was atypic. 



In its normal habitat Cassiopea is subject to considerable changes in 

 salinity, for the density of the inclosed waters in which it lives is undoubt- 

 edly affected by the subtropical heat and rains. The exact changes in 

 density of such inclosed waters and tide-pools is now being investigated by 

 Doctors Mayer and Vaughan. One might have anticipated that Cassiopea 

 would be less susceptible to changes in density, under experimental condi- 

 tions, than hydroids living in the open sea, where the density is practically 

 constant. It nevertheless regenerates exactly like these hydroids. 



REGENERATION OF THE ANNELID WORM AMPHINOMA AFTER REMOVAL 



OF THE NERVE-CORD. 



The following investigation was undertaken in order to ascertain whether 

 the regeneration of the head of the earthworm in the absence of its nerve- 

 cord was a phenomenon peculiar to the earthworm and of no further sig- 

 nificance, or whether other annelid worms living under different environ- 

 mental influences and unrelated to it would regenerate their heads under 

 the same conditions, and thus support the view that regeneration in adult 

 animals is independent of nervous stimuli. 



Two methods for the removal of the nerve-cord of Amphinoma were 

 employed. First, a so-called "window" was removed from the ventral an- 

 terior portion, including muscle-layers, dissepiments, nerve-cord, nephridia, 

 etc. ; second, the nerve-cord was removed with forceps in such a manner as 

 not to injure or only slightly injure the adjoining tissues. The latter method 

 had been successfully employed in experiments upon Lumbricus. The worms 



