

ORGANIZATION AND GROWTH 243 



I II III 



3.3 g. NaCl 3.3 g. NaCl 1.6 g. NaCl 



100 c.c. fresh water 0.03 g. KG1 1.6 g. MgSO 4 



100 c.c. fresh water 0.03 KC1 



100 c.c. fresh water 



No regeneration whatsoever occurred in the first solution; 

 small and not entirely normal polyps formed in the second, 

 but no growth occurred; normal regeneration and growth 

 occurred in the third solution. 



3. It might be possible from these experiments that the 

 MgSO 4 is -essential for regeneration and growth, while KC1 

 is only secondary. I therefore experimented with the follow- 

 ing solutions : 



I II 



2.3 g. NaCl 2.3 g. NaCl 



1.0 g. MgS0 4 1 g. MgS0 4 



100 c.c. fresh water 0.03 g. KC1 



100 c.c sea-water 



No regeneration whatsoever occurred in the first solution; 

 but regeneration and growth were normal in the second. 

 After six days I divided the first solution and the animals 

 contained in it into two vessels, adding 0.05 g. of KC1 to 

 one of them, while I left the other unaltered. The animals 

 contained in the dish to which I had subsequently added 

 the KC1 regenerated and grew in a normal way, while not 

 even a suggestion of regeneration was apparent in the other. 

 The presence of potassium in sea-water is therefore neces- 

 sary for regeneration. 



4. It had still to be decided which constituent of MgSO 4 

 is essential for regeneration in Tubularia. I substituted 

 Na 2 SO 4 for MgSO 4 , and experimented with 300 c.c. of each 

 of the following solutions : 



I II 



2.5 g. NaCl 2.5 g. NaCl 



0.8 g. Na 2 SO 4 0.8 g. Na 2 SO 4 



100 c.c. fresh water 0.03 g. KC1 



100 c.c. fresh water 



