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 asa 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 KCl 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. KCl 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 KCl. 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. KCl. No measurable growth occurred in 
the second solution. The addition of 0.33 g. of KCl to 100 
c.c. of sea-water therefore suffices to prevent growth entirely, 
while regeneration is not stopped until 0.6 per cent. KCl is 
Digitized by Microsoft® 
