248 STUDIES IN GENEEAL PHYSIOLOGY 



This time I distributed the individual animals of a colony of 

 Tubulariae into different vessels, containing 10, 20, 50, 100, 

 and 200 c.c. of sea- water. Each vessel contained six Tubu- 

 larian stems, the roots and polyps of which had been ampu- 

 tated at the beginning of the experiment. The vessels were 

 relatively flat, and only lightly covered with a glass plate to 

 shut out particles of dust that might be carried in through 

 the air. Oxygen could therefore readily reach the sea- water. 

 The first polyps were formed after three days five in each 

 of the vessels containing 100 and 200 c.c. of sea-water, and 

 two in each of the others. Two days later all of the animals 

 had formed new polyps. The inhibition of regeneration was 

 therefore only slight in the vessels containing but a small 

 amount of sea-water. On the eighth day after the beginning 

 of the experiment I measured the growth of the individual 

 specimens, which was as follows: 



In 10 c.c. of Sea-Water In 200 c.c. of Sea- Water 



8.0mm. 7.0mm. 



12.0 8.0 



6.5 13.0 



5.5 9.0 



7.0 10.0 



4.0 3.0 



Average 7.1mm. 8.3mm. 



I obtained about the same average values in the rest 

 of the vessels. Ten c.c. of sea-water therefore contain suffi- 

 cient inorganic material for normal regeneration and normal 

 growth, and variations in the quantity of sea-water above 

 this limit have no effect upon these processes. I have not 

 made experiments with less than 10 c.c., as these barely 

 suffice to cover the Tubularian stems. The result of these 

 experiments is free from the complication which enters 

 into Semper's experiments, in which the animals devoured 

 an uncontrolled (and possibly uncontrollable) amount of 

 vegetable food. 



