426 THE KEEPER'S BOOK 



was the female, while his milt is allowed to run over the 

 eggs in the basin. A slight pressure near the vent is 

 necessary to start the flow of milt. A very few drops is 

 sufficient to fertilise the mass, and one male will fertilise 

 the ova of several females. But it is poor economy to be 

 niggardly if males are plentiful, and, on the other hand, 

 to be extravagant if males are few. In any case it is 

 good policy to retain all superfluous males until the day's 

 work is over. Hence the practical utility of the small 

 bag-nets. After depositing the milt on the eggs, which 

 at this stage are all separate, the operator stirs them 

 gently with the tail of the male fish. He in turn is then 

 liberated, or kept captive for further service if required. 

 The eggs are then covered with water an inch deep 

 over them, and in a few minutes another quarter of 

 an inch of water is added. The eggs meantime have 

 coagulated in mass. Then the basin must be left per- 

 fectly still for a time, which maybe anything from twenty 

 minutes to two hours, according to temperature. During 

 this time the mass will be disintegrating, and any dis- 

 turbance must be avoided. Now and again the operator 

 may look carefully to see if the eggs are separated, when, 

 if they are, the process of fertilisation is over and they 

 may be washed clean of milt by gently pouring water 

 over them. When they are quite clean, the eggs will 

 be found to have changed their former rich salmon-pink 

 to an opalescent hue, which indicates that fertilisation 

 is complete. The same procedure is gone through with 

 other fish, and as each lot of ova is fertilised and cleaned 



