THE EFFECT OF DISTILLED WATER UPON THE 



FIDDLER CRAB. 1 



J. F. ABBOTT. 



At present, Fundulus offers the only exception 2 to the state- 

 ment that the unprotected epithelial surfaces of marine and 

 fresh-water animals are permeable to distilled water and to 

 electrolytes in solution. In all cases life appears to be preserved 

 by some sort of an "adaptation" as yet unexplained which 

 limits the permeability or controls it so as to maintain the 

 integrity of the body fluids. Sumner 3 has shown that the gills 

 in a variety of Teleosts are permeable, and Scott and White 4 

 have conclusively shown the same thing in Mustelus, while Garrey 5 

 and others have demonstrated the fact in a great number of 

 invertebrates. The apparent exception offered by Fundulus is 

 therefore the more remarkable. 



While working at the Beaufort Laboratory of the U. S. Fisheries 

 Bureau my friend Professor W. E. Garrey called my attention to 

 the fact that the fiddler crabs (Uca pugillator} which abound in 

 that region were passing indifferently from the sea to the overflow 

 of an artesian well and he suggested that this form, like Fundulus, 

 might offer an exception to the statement just made regarding 

 the permeability of membranes. A few tests seemed to confirm 

 this, for the crabs appeared to live indefinitely in pure distilled 

 water as well as in salt solutions of various osmotic densities. 

 The writer therefore devoted the greater part of the past summer 

 to a study of the reactions of this animal to various salt solutions. 

 For the privilege of working at the Beaufort Laboratory he is 

 indebted to the kindness of the Hon. George M. Bowers, \j. S. 

 Commissioner of Fisheries, and to Mr. Lewis Radcliffe, the 



1 From the Laboratory of the U. S. Bureau of Fisheries at Beaufort and the 

 Zoological Laboratory of Washington University. 



2 Species of Cyprinodon and Gambusia apparently behave in the same way, 

 although the facts have not been thoroughly worked out. 



8 U. S. B. F. Bull., 1905, Vol. 25, p. 97. 

 4 Science, N. S., 1910, Vol. 32, p. 767. 

 6 Biol. Bull., 1905, Vol. 8, p. 257. 



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