A CO-OPERATIVE BREATHING SOCIETY. 57 



packed at this stage, and so well do they travel that the loss in 

 one consignment to Newfoundland of over one hundred thousand 

 this season 1885-86 was under fifty eggs, or less than '005 per 

 cent. The 



COMPLETION OF THE EMBRYONIC CIRCLE 



immediately precedes hatching. The tail curls round generally to 

 the right, and passes the nose. The body of the embryo has now 

 become dark, the yolk globules have mostly collected immediately 

 below the stomach. The yolk-sac circulation, though still lacunar 

 in many parts, follows well-marked lines. In the case of twins it 

 is common to both. The caudal pulse is well marked, and the 

 motion of the pectoral fins easily discerned. A very slight rise 

 in temperature will cause the eggs to hatch instantaneously. At 

 Howietoun, when the eggs are washed off the grilles on to the 

 bottom of the box, sometimes 90 per cent, will hatch in the 

 first half-hour. 



When a lot of eggs are ready to hatch, the grilles are taken out 

 of the boxes, and all unimpregnated eggs and any puny embryos 

 removed. The hatching-boxes are next stripped of their fittings, 

 thoroughly cleaned, and the safety-screens fixed 13 inches above 

 the outlet. If the ova is on the point of hatching it is then 

 laid down on the wood. It is often convenient to prepare the 

 boxes a few days before the eggs are due to hatch ; and since, if the 

 eggs remained many hours in the comparatively still water at the 

 bottom, some of the embryos would be drowned, a small piece of 

 tile is laid in the box, and a couple of grilles balanced on it until 

 the hatch commences, when the tile is taken out, and the grilles 

 reversed and removed. With 3 inches of water in the hatch- 

 ing-boxes there is no danger of the alevins becoming suffocated a 

 very common source of loss in badly constructed trays. 



A CO-OPERATIVE BREATHING SOCIETY. 



Shortly after hatching the alevins congregate together in dense 

 masses in the corners and against the sides of the hatching-boxes. 

 If the water over these masses be slightly discoloured so as to 



