430 THE KEEPERS BOOK 



and simmer, and any dead or barren egg, being lighter, 

 will come to the top. It can then be picked out with 

 the syphon tube. So too any foreign substance will 

 show up at once in the mass. 



The only occasion for real anxiety at this period is 

 during a spate, when a large proportion of matter held 

 in suspension in the water may be expected to be de- 

 posited, if not on the eggs yet in the boxes. Of course 

 the best means to prevent this is careful filtration, first 

 at the source of supply, and again, if convenient, within 

 the hatchery. But, notwithstanding, the boxes will still 

 require occasionally to be cleaned. This can be done 

 without injury to the eggs, but, as great care is necessary 

 in the moving, cleaning with clear water, and replacing 

 them, not to mention the cleaning of the boxes, it is a 

 troublesome enough business. The danger of a deposit 

 on the eggs is that it prevents the free absorption of 

 oxygen from the water through the shell of the egg, and 

 the free giving off of the carbonic acid gas generated 

 by the growth within, resulting in suffocation and death 

 of the embryo. 



Periodical inspection should also be made at this time 

 of the intake chamber of the water supply, and the rose 

 of the main pipe examined to see that no floating matter 

 has got in to foul it. Decayed leaves are often trouble- 

 some in this respect. 



With ordinary care all the eggs will duly hatch out 

 at the appointed time, when our young fish will have 

 reached the alevin stage. 



