224 STUDIES IN GENERAL PHYSIOLOGY 



went no farther. I now divided the concentrated sea-water 

 and the animals contained in it between two vessels, and 

 added enough distilled water to one of them to restore it to 

 the concentration of normal sea-water. After a few days 

 all the animals in this vessel regenerated their polyps in an 

 entirely normal manner, but no regeneration whatsoever 

 occurred in the other. I have repeated this experiment sev- 

 eral times, always with the same result. While, therefore, 

 a great lowering of the concentration of the sea-water (33J 

 per cent.) not only does not inhibit regeneration, but may 

 accelerate it, an increase in the concentration to a like 

 amount suffices to prevent regeneration altogether, or almost 

 entirely, without, however, injuring the power of regenera- 

 tion, provided the animal does not remain too long in the 

 concentrated solution. 



3. In order to determine the limit of concentration in 

 which regeneration is possible, I evaporated normal sea-water 

 to 90, 80, 75, 70, 60, and 50 per cent, of its volume. The 

 solutions were filtered and shaken for some time in the air. 

 Regeneration took place in the first three solutions, but not 

 in the last three. Regeneration, however, did not occur 

 simultaneously in the first three solutions, but the more 

 slowly, the more concentrated the solution. After lying for 

 several days in the 70 per cent, solution, the Tubularise had 

 not lost their power of regeneration, but in the stronger 

 solutions even this had suffered. When the Tubularians 

 were brought back from the stronger solutions into normal 

 sea-water, they no longer formed polyps. The tissues of 

 the stem were shrunken and often separated from the peri- 

 derm. Upon the other hand, when I added as much as 50 

 per cent, of distilled water to ordinary sea-water, a distinct 

 inhibition of the process of regeneration could not once be 

 noted; only upon the addition of 100 per cent, of distilled 

 water did regeneration cease. If still more distilled water, 



