W. RUSHTON 73 



either milt or eggs till the two were brought in contact in the presence 

 of the effluent under examination. 



Ten eggs were taken up in each case and submitted to the various 

 effluents with a measured quantity of milt and the two left in contact 

 for 30 minutes to ensure uniformity throughout. 



Some of the milt was examined microscopically at the same time and 

 the length of time before activity ceased was noted. 



It is known that the milt of trout will remain in good condition and 

 fertiUse ova 24 hours after extraction if kept free from moisture, i.e. if 

 care is taken in extraction that no drainings or drippings from the male 

 fish are allowed to come in contact with it; but if brought in contact 

 with water they at once become very active and lose their fertilising 

 power after three minutes' activity so that the period of activity is very 

 short. This experiment can easily be done by taking a series of drops of 

 milt on a shde side by side and adding the smallest drop of water to each 

 and the time of activity taken. 



It is further known that some spermatozoa of fish are more sensitive 

 to poisons than young or mature fish and may be killed by such small 

 amounts of poisons as can be detected only by very refined chemical 

 methods. 



Sample 1. Water from the upper reaches of the stream before any 

 effluent had entered. 



Colour ... ... None. 



Reaction ... ... Neutral cold or hot using phenol-phthalein 



indicator. 

 Activity of sperms Three minutes. 

 Eggs all fertihsed and gave rise to normal embryos 90 per cent, of 

 which hatched. One year and one two-year-old trout remained ahve in 

 this sample for over a week when they were removed to fresh water. 



Sample 2. Containing effluent from one distillery. 



Colour ... ... None. 



Reaction... ... Neutral hot or cold. 



Sperms ... ... Active for 2 to 3 minutes. 



Eggs all fertihsed and gave rise to normal embryos 90 per cent, of 

 which hatched out. 



Sample 3. Diluted sample from a woollen mill where wool-scouring 

 takes place. 



Colour ... ... SUghtly yellow. 



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



Sperms ... ... Active 2 minutes. 



