ORGANIZATION AND GROWTH 227 
amount of salt contained in the sea-water is counted as NaCl. 
Our previous experiments had, indeed, shown that the con- 
centration limit for regeneration in Tubulariw is reached 
when 100 c.c. of sea-water is evaporated to 70 c.c. 
The second table gives the results of an experiment which 
shows the difference between the effect of increasing and 
decreasing the concentration of the sea-water. Each solu- 
tion contained six animals. The percentages indicate the 
volume of normal sea-water, + indicating an increase, — 
indicating a decrease, in the amount of water contained in it. 
The figures indicate the percentage by which the original 
volume has been increased or decreased. 
TABLE II 
Date ~26% | 21%) 8% |Normal | t60% | +50 % | +70% | -+100% 
Third day..... 0 1 2 4 4 1 0 0 
Fourth day....| 0 5 6 6 6 6 5 4 
Fifthday...... 3 6 6 6 6 6 6 6 
I continued my observations for two weeks, but no regen- 
eration occurred in the most concentrated of these solutions 
(—26 per cent.) beyond the three animals mentioned in the 
table. 
7. The facts of this chapter may be shortly summed up 
in this: an absorption of water is essential to regeneration in 
Tubularia (and probably all animals). If the absorption of 
water is limited by keeping Tubularia in concentrated sea- 
water, regeneration is retarded, and finally completely inhib- 
ited, by even a slight increase in the concentration. Regen- 
eration is, however, not only not retarded but, if anything, 
accelerated, if the Tubularians are put into diluted sea-water. 
Only when the dilution exceeds a certain limit and the 
tissues are flooded with water a retardation of the regenera- 
tion occurs. While a decrease of 30 per cent. in the orginal 
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