SOME EFFECTS ON FUNDULUS OF CHANGES IN THE 

 DENSITY OF THE SURROUNDING MEDIUM. 



GEORGE G. SCOTT. 



Bert, '71, found that certain teleosts changed in weight on 

 being immersed in water having a different density from that of 

 the normal medium to which they were accustomed, though in 

 some cases death occurred before any considerable change in 

 weight had taken place. Garrey, '05, found that 80 per cent, of 

 Fundulus heteroditus taken from sea water lived in fresh water for 

 six weeks. Loeb, 'oo, said, "Fundulus can be thrown from sea 

 water into distilled water without any considerable swelling or 

 without any visible injurious effects." Sumner, '06, reported a 

 series of experiments from which he concluded that Fundulus did 

 not survive transference from sea water to fresh w r ater. He also 

 concluded that diluted sea water containing only 2 per cent, to 

 4 per cent, of the salinity of pure sea water had a salutary 

 influence on the preservation of life. Since the osmotic pressure 

 of fresh water is but little less than this diluted sea water and 

 since Fundulus survived in this solution but not in the other, 

 Sumner concluded that the question of survival or death is not a 

 question of difference in osmotic pressures. Sumner also investi- 

 gated the changes in weight undergone by Fundulus in different 

 dilutions of sea water. He found that in fresh water there was 

 a slight gain which was followed by a loss until near the normal 

 weight. In general transference to a hypertonic solution resulted 

 in loss of weight, while in hypotonic solutions there was noted a 

 gain in weight. And yet the change in weight bore no constant 

 ratio to the changes in the osmotic pressure of sea water. Sumner 

 found indications of a smaller gain in Fundulus from Woods Hole 

 than in those from the New York Aquarium. He accounts for 

 this as being due to differences in the physiological state of the 

 organism at the higher temperature of the summer months. 

 Their more active metabolism at this period might account for 

 the greater permeability. On account of the diverse position 



121 



