94 Papers from the Marine Biological Laboratory at Tortugas. 



media regenerated at a slow rate and threw out masses of slimv material, a 

 reaction commonl_v shown when this animal is placed in disagreeable sur- 

 roundings. It is recognized that the concentration and dilution of these sea- 

 water preparations are very great and w-ith slight concentration or dilution 

 such injurious effects might by no means follow. The one object of the 

 powerful solutions was to ascertain whether this animal was very resistant 

 to changes in the osmotic pressure conditions, and the fact that they existed 

 in these solutions for such long periods of time indicates that they are not 

 particularly sensitive to osmotic changes. 



Table 6. — Rates of regeneration in strange chemical environments. 



* Back to sea-water. 



t Dead, 



t The cut on this individual is differently shaped, see the 



§ The CaClo caused a slight precipitate to form in the sea 



I Tetanus, put into sea-water. 

 * In sea-water, 

 tt Put into sea-water. 



text, 

 water 



solutions. 



A close study of the tables indicates that NaCl slightly retards the 

 regeneration rate, but the weakened appearance of the disk in the strengths 

 of this medium used suggests that the retardation is not a direct effect of 

 the Na, but more probably due to the animal's loss of tone. 



The stronger solutions of KCl also retard regeneration. The weaker 

 solutions, on the other hand, seem to accelerate the process so that the 

 specific amount of regeneration from individuals subjected to their action 

 is slightly greater than that of the control medusas. 



The medusae in the KCl solutions have their disks fully expanded, but 

 their mouth-arms are contracted and balled up in the center. 



The CaCl, solutions produce a tendency toward tetanic contractions 

 and in the stronger solutions the oral surface of the disk is often torn by 

 this violently contracted condition. Mayer (1906) has called attention 

 to this effect of CaCL on Cassiopea. The rate of regeneration in all of the 

 CaCU solutions was slower than normal. 



