FUNDULUS AND THE SURROUNDING MEDIUM. 123 



On July 10, 1908, I transferred ten Fundulus heteroclitus 

 through a series of changes from sea water to a large rectangular 

 dish containing about 20 liters of fresh tap water. In the bottom 

 of the dish was placed some gravel from the shore near by the 

 gravel having been thoroughly washed in tap water. The water 

 in the tank was completely changed every day or so and once 

 a week the tank was thoroughly cleaned. Food was placed in 

 the tank daily, but all uneaten portions were removed after a 

 few hours. On the whole the fishes did not seem eager for the 

 food. Most of the fishes died during the next three or four weeks 

 but one fish was alive and apparently in good condition on 

 September 8, 1908, sixty days after the beginning of the experi- 

 ment. A rough test of the water toward the end of the period 

 showed a slightly greater amount of chlorine than was present 

 in fresh water. And yet the hydrometer recorded a specific 

 gravity of about i.ooo. At first we might think that Sumner's 

 contention as to the life-saving action of a small amount of salts 

 was borne out here. But the amount of salts in which this 

 specimen survived was less than that claimed by Sumner as 

 necessary to exert a life-saving action. At the same time I do 

 not wish to disclaim Sumner's contention. I only wish to point 

 out a case where this conclusion does not follow. 



Not only will Fundulus survive transfer to fresh water, but 

 regeneration of removed tissues takes place under these condi- 

 tions. This is shown by the results of the following experiments 

 carried out with Fundulus heteroclitus taken from the New York 

 Aquarium from the diluted harbor water which had a specific 

 gravity of about 1.012 (sea water having a sp. gr. of 1.025). 

 The caudal fin was removed in the same manner as described 

 in a former paper by the present author (Scott). After the 

 removal of the fin the fishes were transferred gradually to fresh 

 water in a large rectangular jar which was constantly aerated 

 from the compressed air supply in the laboratory at the College 

 of the City of New York. The water was siphoned off nearly 

 every day and replaced by a fresh supply from the tap. Fresh- 

 water plants were kept in the experimental aquarium during the 

 latter part of the period. The specimens were fed with fish 

 food which they soon learned to take. I was not concerned at 



