ORGANIZATION AND GROWTH 245 



XIII. FURTHER OBSERVATIONS ON THE EFFECT OF DIFFERENT 

 SALTS UPON REGENERATION AND GROWTH IN TUBULARIA 



1. According to Hoppe-Seyler, potassium has a poisonous 

 effect upon higher animals when introduced in too large 

 amounts into the food. I have already shown that after the 

 addition of 1.3 per cent. NaCl to sea-water, regeneration is 

 still possible, but not growth. With this as a starting-point, 

 I investigated whether regeneration is still possible after the 

 addition of 0.6 g., 1.0 g., 1.3 g., and 1.6 g. of KC1 to each 100 

 c.c. of ordinary sea-water. An opaque precipitate was imme- 

 diately formed at both cut ends when I introduced Tubu- 

 larian stems into the two most concentrated of these solutions. 

 In not one of them did regeneration occur. After eight 

 days I returned a number of these animals which had been 

 in the potassium-chloride solutions to normal sea-water, in 

 order to determine whether they were dead, or whether 

 regeneration had only been inhibited in them. The animals 

 returned from the 0.6 per cent, and 1.0 per cent. KC1 solu- 

 tions to normal sea- water regenerated and grew in this ; the 

 remainder, however, were dead. 



I now added to each 100 c.c. of sea-water 0.16 g. and 

 0.33 g. of KC1. In the weaker of these solutions all the ani- 

 mals regenerated, but much more slowly than the control 

 animals of the same colony kept in ordinary sea-water. In 

 the second solution only four of the nine animals regenerated. 

 Growth was also much diminished. While longitudinal 

 growth in the animals kept in the normal sea-water amounted 

 to 11 mm. upon the average, it amounted to only 1 mm. in 

 the same time and at the same temperature after the addition 

 of 0.16 per cent. KC1. No measurable growth occurred in 

 the second solution. The addition of 0.33 g. of KC1 to 100 

 c.c. of sea-water therefore suffices to prevent growth entirely, 

 while regeneration is not stopped until 0.6 per cent. KC1 is 



