SOME PHYSIOLOGICAL DISTINCTIONS BETWl.l A 

 I RESHWATER AND MARINE ORGANISMS. 



EDWARD F. ADOLPH, 

 FROM THE MARINE BIOLOGICAL LABORATORY, WOODS HOLE. MASS. 



I. 



Aquatic organi.-ms are in general distinctly divided into those 

 species inhabiting fresh water and those inhabiting sea water. 

 Yet thi- division i- evidently not a phylogenetic one, since closely 

 related spn ;< - live in either (Ouinton. '04). Only in a few 

 -perie- ,ire the -ame individuals capable of pa ing from one 

 medium to the other. The transition /ones of brackish water 

 are relatively small in extent and very variable, still there are a 

 feu or.;. mi-ins which thrive only in such diluted -ea water. 



Particularly the distribution of fishes betueeii fresh water and 

 863 u.itii has excited the interest of biologists. Paul Mert tried 

 to find uhy tish died when taken from their u-ual medium and 

 placed in the other ('71. '7.}). For marine animals In 

 reached one important conclusion, namely, that the toxic rilei \ 

 ua- not aluay- due to the dilution of the substances di: ol\cd 

 in sea \\ater. This conclusion has been thoroughly confirmed 

 by the sub-equent observations of Loeb ('03 and others. 



Practically no further analysis of this problem could be made 

 without careful quantitative studies. Such were undertaken by 

 Sumner i'o< upon marine teleost fishes. He found significant 

 changes in the \\atercontent and in the salt content of the animals 

 durinji their immersion in diluted sea water. Thus the dele- 

 terii'ii- effect -reined to be a loss of essential body constituent-, 

 because the animals were unable to regulate fa\i-rably their 

 integumental permeability under the new circumstances. 



Meanwhile a new line of attack came to light with the discovery 

 of salt antagonisms by Ringer ('82). Loeb ('oo) found that 

 marine organisms were readily affected by the disturbances of 

 the balance between salts, but were almost independent of 

 osmotic pressure changes. Thus ('03), the marine crustacean 

 Cuitnmarus endured dilution of the seawater medium just a- well 



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