ARTIFICIAL PROPAGATION 187 



working, to " heap " additional eggs in the zinc baskets. Indeed with 

 water highly oxygenated, three full layers of eggs can be apportioned 

 to each basket, which would raise the number of eggs treated in each 

 hatching box to over 40,000. There is, however, little use in taking 

 risks, for, the closer the eggs are massed, the more oxygen and the more 

 constant attention will they require, and, even with the greatest care, 

 the death-rate of eggs would largely increase. 



It is clear, then, on a comparison of the two systems, that, neglecting 

 the inevitable death-rate which occurs under both systems — that of the 

 grilles being not so much less as to make it a factor in one's choice— the 

 " grille " system requires at least as much as four times the space 

 required by the " basket " system for convenience of working. But — • 

 and this is a very important " but " — while eggs may be hatched out 

 successful 1)- with no more water pressure than will deliver 3 gallons 

 per minute to a box containing 10,000 eggs laid on glass grilles, the 

 same flow of water will not serve the 40,000 eggs distributed in each 

 box over sixteen zinc baskets. Some supplementary system of water 

 aeration or delivery must be adopted, and that can generally and 

 practically be got only from a gravitation water supply giving pressure 

 sufficient to provide independent sprays or jets for each separate basket. 

 The available water supply will therefore be the decisive factor dictating 

 the ado[)ti()n of one or other system, the question of space being 

 relatively of but secondary importance. 



To revert to construction, this has to be added, that all woodwork 

 must be carefully charred; that every separate piece must be carefully 

 smoothed and exactly fitting, without the least projection or crevice; 

 and that all zinc should be varnished by a special varnish which can be 

 obtained from any of our commercial hatcheries. 



Let us assume now that everything in the hatchery is prepared for 

 the reception of the ova. All the taps are in working order, ready to 

 be turned on or off as occasion requires; a stead}' flow is left running; 



