EFFECT OF DISTILLED WATER UPON THE FIDDLER CRAB. 173 



Crab No. 4 died shortly after 7th hr.; final chloride determination not taken. 

 Crab No. 5 died shortly after ?th hour. 



It will be seen that without exception all the crabs gained in 

 weight through immersion in distilled water. Likewise all the 

 crabs lost chlorine, presumably through diffusion. There is no 

 doubt that some of this loss may have been occasioned by bleed- 

 ing, yet the outer shell of the gill chamber is very little vascular 

 and such a loss must be inconsiderable. It, however, might be 

 sufficient to account for the irregularities in the amounts of 

 chlorine lost by the various crabs. An exception must be made 

 of Crab No. 3 of which the branchiostegite was cut away very 

 deeply and bled into the water. This accounts for the very 

 small gain in weight and exceptionally high chlorine loss. Yet 

 this individual for some reason not evident lived longer than 

 any of the others. 



If death is brought about by the extraction of necessary salts 

 from the organism it ought to make considerable difference 

 whether the amount of water that surrounds the animal is great 

 or small. For we have seen that the presence of a very smalt 

 amount of salt in the water (such as exists in ordinary well water) 

 is sufficient to preserve the membrane or at least to greatly 

 retard its solution by the water. If the amount of water were 

 scant the crabs might be able, by losing a small amount of salts 

 to it and thus raising the osmotic density of the medium ever so 

 slightly, yet thereby to retard the solvent effect of the distilled 

 water on the gill membranes. To test this, fifty tall, wide mouth 

 bottles were arranged, in each ten of which was put, respectively, 

 50 c.c., 100 c.c., 150 c.c., 200 c.c., and 250 c.c. of distilled water. 

 In each bottle was placed a crab (U. pugillator}. The gill cham- 

 bers were not opened but the lot were subjected to running fresh 

 water for fifteen minutes, a procedure which experience has shown 

 displaces practically all the salt water that may be retained in 

 the gill chamber. The results are tabulated below, the figures 

 representing the number of crabs alive at the different intervals 

 of time. 



