246 STUDIES IN GENERAL PHYSIOLOGY 
added. In doses of 1.3 g. to 100 cc. of sea-water it is fatal 
to Tubularia. 
2. KNO; inhibited growth when 0.6 g. was added to 100 
c.c. of sea-water; regeneration was prevented by the addition 
of 1 g. of KNO; to 100 cc. of sea-water. NaNO; had a 
weaker effect; regeneration still followed the addition of 1.3 
g. to 100 c.c. of sea-water; but when 1.6 g. of this substance 
was added, regeneration did not occur. An experiment on 
growth gave the following average results; ten specimens 
were used in each case; the experiment lasted eleven days, 
and the temperature was about 16° C. 
Average Growth 
In normal sea-water - 7.3 mm. 
Addition of 0.6 per cent. NaNO3 11 
Addition of 1.0 per cent. NaNO3 0.38 
The greater effect of the potassium over the sodium is less 
apparent in this experiment than in the chlorine compounds 
of this metal. 
3. The poisonous action of NH,Cl upon Tubularia is very 
striking. An opaque precipitate is formed at both ends of a 
Tubularian stem when only 0.06 g. of NH,Cl is added to 100 
c.c. of sea-water. A quantity 0.03 g. to each 100 c.c. of 
sea-water suffices not only to inhibit all regeneration and all 
growth, but renders these life processes forever impossible; 
for when the animals are returned from such a solution to 
normal sea-water, they no longer regenerate and grow. 
4. In conclusion I wish to direct the reader’s attention 
to Fig. 62, which shows the regeneration and growth of 
three Tubularian stems taken from the same colony. 
They had been put into different salt solutions for the 
same length of time at the same temperature. ab is in 
all cases the original piece cut from the animal. Fig. A 
remained in ordinary sea-water. The piece bd had grown at 
the oral end 6, the piece ac at the aboral end a; the polyps 
were very sturdy. The diameter of the new stem is nearly 
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