74 Co7itrihutions to the Biology of Freshwater Fishes 



Ova fertilised and gave rise to normal embryos; 85 per cent, hatched 

 out. 



Sample 4, From same place as 3, but taken a few hours later; 

 similar results to 3, but sample a httle more alkaUne. Two yearling trout 

 introduced into these samples, although they showed uneasiness at first, 

 soon settled down to the unusual conditions and were alive four weeks 

 afterwards and during the period showed no unusual symptoms. 



Sample 5, Taken from below the sewage outflow after crude sewage 

 had entered the stream. 



Colour ... ... Yellow. 



Reaction ... ... Neutral cold, alkaline hot. 



Sperms ... ... Lived only 1-75 minutes. 



Ova fertilised and gave rise to normal embryos in fresh water in four 

 cases only. The effect on yearling fish was very marked with this sample. 

 As soon as the fish were introduced they showed signs of trouble at once. 

 The jaws began to move actively, attempts at leaping out of the hquid 

 were very frequent, then after 5 minutes a period of rest at the bottom 

 of the vessel, the fish appearing to be exhausted, then further attempts 

 at coming to the surface were made with gradual sinking to the bottom 

 again. This continued for 15 minutes, when the fish showed signs of 

 turning on their sides and within a few seconds were on their backs. 

 Then spasmodic darts took place in an aimless manner which continued 

 periodically for about an hour when the fish died. 



Repeating this experiment but removing to fresh water at the first 

 signs of turning over it was found possible to recover them and in a few 

 days they acted quite normal. 



Diluting this sample 1 in 4 the period of being overcome was 

 lengthened, but the final result was the same. 



Sample 6. This was from the same source as 5, but taken from the 

 outflow pipe before it entered the stream. 



Analysis of this sample showed it to be crude sewage. 

 Colour ... ... ... Brown. 



Reaction ... ... Distinctly alkahne cold or hot. 



Smell Very offensive, ammonia, sulphuretted 



hydrogen prevaihng. 

 Analysis ... ... ... Parts per 100,000. 



Free and sahne ammonia 5-6. 

 Albuminoid ammonia ... l-l'l. 

 Oxygen absorbed in two 



hours at 27° C. ... 8-9. 



