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 Tubular ia3 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, -f 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 



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 



