American fisheries Society. 87 



It happened that the troughs intended for the summer use of 

 these fish were not quite ready when the eggs were hiid out in 

 March to hatcli, and thev were therefore crowded for hatching 

 into a smaller number of troughs which were for the purpose 

 divided into compartments by fine, close-fitting wire screens. 

 The water, passing first over lot A would nourish in succession 

 lots B, C, D and so on down the trough. 



One of the most noticable results was that the losses were 

 very unevenly distributed in the troughs. For instance. Lot A, 

 at the head of the trough, might be half destroyed. Lot B totally, 

 and Lot t' almost ^\■holly escape. When all the results Avere cor- 

 rellated, it was found that the mortality ran in families, some 

 families being utterly destroyed, some suffering moderately, 

 while in otliers the mortality would l)e so light as to warrant the 

 •conclusion that the epidemic had nothing to do with it. 



Now what shall we say ? Did the germs of the disease come 

 to these little fishes from their parents, or did they inherit merely 

 different resisting j^owers, so that, though all of them were 

 assailed about equally by the disease-germs, some of the families 

 had a hereditary ability to ward them off, while others suc- 

 cumbed? The answer to this question must await deeper study 

 than we have yet been able to give. 



Among other deductions to be drawn from the same data is 

 one as to the infectiousness of the disease. Infectiousness would 

 cause the lots occupying the lower parts of the troughs to receive 

 the disease from those lying aljove them ; but the record shows 

 that nothing of the sort happened. The rate of mortality of the 

 lower lots was wholly uninfluenced by the condition of those 

 above. It was therefore not an infectious disease, and did not 

 spread from lot to lot. 



It was further observed with reference to this disease, that 

 the occasion of its first appearance was coincident with a great 

 reduction in the proportion of lake water in the hatchery su])ply. 

 A coffer dam had been constructed at the outlet of Craig pond 

 (or lake) which in the spring shut off the lake water and com- 

 pelled us to use a much larger proi)ortion of spring water. K 

 second attack in 1893, was coincident with a very low stage of 

 Craig pond and brook, caused by a scanty fall of rain and neg- 

 lect of storage measures. It therefore seemed reasonable to turn 



