138 



FISH FARMING I 



striction all that has to be done is to lift the egg out of the 

 water and then press tha indiarubber with the thumb, as 

 before, when the egg is immediately released and falls from 

 the tube. In practice the process is most simple. 



Another very useful little article in the hatchery is illus- 

 trated by Figs. 39 and 40. A plain glass tube, fin. inside 

 measurement, is slightly bent, as shown in Fig. 39. When 

 used asi a. syphon it is very handy for examining alevins, more 

 especially in their advanced stages, as it permits of them 

 being contained in the bend of the tube and in a quantity of 

 water sufficient to allow them to swim and dart about. The 



Fig. 39. Glass Hand Syphon. 

 Fig. 40. Section of Hand Syphon. 



level of the water contained in the tube is shown by the dotted 

 line A B in Fig. 40. 



Be careful, and guard against sediment. A very slight 

 amount of this! which may be carefully washed off by a 

 gentle depression, or raising, or rocking of the tray is not 

 of vital importance ; but it is best absent altogether, there- 

 fore, if the slightest sign of it is discovered, remedy the evil 

 at once in the settling tank or in the filter. When the eggs 

 are further advanced towards hatching, and may be tho- 

 roughly washed (preferably by means of an ordinary garden 

 watering can) without harm resulting, sediment is an item 

 of smaller importance; but even then it is better absent. 

 Guard against shaking the eggs from twenty-four hours after 

 laying them down till they are eyed. I have previously 

 explained that the period of incubation varies with the tern 

 perature of the water; but, in a suitable temperature, which 



