56 WORK IN THE HATCHING-HOUSE. 



shortly to be occupied by the principal duct of the yolk-sac 

 circulation, and the right side gradually disappears. From the 

 early or late appearance of this triune, and by the rate of its 

 passage round the hemisphere, the vitality of the embryo can 

 be accurately presumed. The ova in this stage will bear very 

 little handling, and should be examined without contact. A 

 lucifer match placed close to the surface of the water is a good 

 and expeditious way. The 



EYE STAGE 



marks a still further development, and although neither colour nor 

 red blood are present, the eggs may be safely handled ; this is 

 the best time to pack ova for the antipodes. The tail is in this 

 stage free, and, by holding the egg up to the light in a warm 

 hand, it will move slightly generally to its own right. 



Breathing on the egg will cause the same effect, and is a con- 

 venient test when the hands' are cold. It is, however, very 

 important not to pack ova until the movement can be discerned in 

 the tail. The next stage is marked by the 



FIRST APPEARANCE OF. RED BLOOD. 



The eye-spots simultaneously show black colour, and the eggs will 

 now stand any fair usage ; they may even be dropped on the 

 floor, and picked up again without injury. One half of the period 

 of incubation is completed ; all the unfertilised eggs show the 

 annular disc clear and hard. A few of the imperfectly fertilised 

 still show a disc with a hard centre, but these will turn white in 

 transference from the trays, and even if a few survive, they are 

 easily recognised. The only eggs which cause any anxiety are those 

 nearly, but not quite sufficiently, fertilised, which are difficult to 

 tell at this stage. They may be divided into two heads, those 

 with small and very black eyes, and those with ordinary-sized eyes 

 but of a very red colour. However, as insufficient impregnation 

 occurs almost solely in experimental work, or in the eggs of young 

 trout, little inconvenience occurs from this cause in a well-regulated 

 trout-farm. Eggs for America or the continent of Europe are 



