EFFECTS UPON FISHES OF CHANGES IN SALINITY OF WATEK. 83 



fresh-wutPi- species, and Fi,„<hil,i.s h,t, rn,r,1 ,is. tlie tDinooil {Mn-rn,j.i,hix to,„- 

 r<i(T). and the sea raven {ll,:iiiifi'ijtf,rns <tiiii /■innni.t) among tlie salt-water ones, 

 were used. The more sensitive species were allowed to die out of water, while 

 the more resistant ones were killed by vapor of chloroform. Tlie tishrs were 

 weighed first before immersion, again after 3 to 5 hours of soaking in the 

 solutions, and once more after another interval of about I'l hours. Seven 

 sorts of water were employed- fresh water, and salt solutions having the 

 densities I.OOl'A. l.on:,. I. old. l.ol."). l.Oi'o. and I.OlTi. These solutions were 

 prepared with a coninicnial ""sea >.alt." It was found that the salmon, carp^ 

 and Fii/iiliiJiix all increased" from the first in water of all grades. This was 

 practically true of the suntish and tomcod likewise, except that during the iirst. 

 interval there was no appreciable increase (in one case a slight decrease) in tiie 

 three stronger solutions, an increase following, however, during the next 13 

 hours. The sea raven alone gave results which conformed in some measni-e 

 with what one would expect from osmotic action. Here a loss occurred in the 

 three stronger solutions (1.015, i.(t20, and 1.025) during the first 3i hour.s, 

 this amounting to 1 per cent in the tirst case and 1.8 per cent in the last. 

 YA'i^n with this species. how(»ver, there were irregularities whicii confused the 

 results. 

 Krj,rrh,...t7S. 



In this additional experiment with ( hir,,rhijii<-}nis. in which fresh water and 

 two different strengths of salt water were used ( l.oos ami l.ol4). a gain 

 resulted in each case, though in the third ease this was not certain daring the 

 tirst day. 

 This increase in weight of dead tishes in the foregoing experiments is in striking- 

 contrast to those cases (pai'ticularly 41, <^, and 55, (■) in which fishes of the same 

 species dying in strong salt water lost weight in considerable measure. The follow- 

 ing two experiments likewise illustrate this contrast: 

 Erptriment 7 'J. 



Specimens of the tautog, sea raven, and tomcod, which after death were i)ut 

 into water of density l.(il-f, were all found to have increased in weight at the 

 end of IS hours. 

 Exp, r III lent HiJ. 



A living tautog put into a tul) of water of about the same density lost l.S 

 per cent during the tirst 20 hours, although death from asphyxiation occurred 

 some time during this period. It is true that the dead tish underwent an 

 additional decrease of about one-half per cent during the next 2-4 hours, ])ut 

 the loss of mucus through wiping the fish perhaps more than accounts for this. 

 Tlu! increase in weight of dead fishes in solutions w hicli are undoubtedly hyper- 

 tonic as compared with the body fluids maj- be explained in a number of ways. It 

 is, of course, possil)le that water enters the alimentary canal at either end; or it is 

 possible that after death the limiting memliranes of the body })ecome so completely 

 permea))le that no osmotic action is possible, and that a process of imbibition occurs, 

 the water cond)ining in some way, perhaps, with the dead proteids of the tissues. 

 The latter hypothesis seems to me to be far more probable, since the gain in weight 



n Percentages of increase or decrease are omitted here as being of little importance for the i>resent discnssion. 



