METHODS OF HATCHINO FISH EGGS. 
213 
nearly to the metal plate (Fig. 3), turn on a full head of water, and the air in the feed- 
tube will pass in bubbles above the eggs, leaving the jar by the outlet-tube. The eggs 
will not be disturbed. After the air is all out, close olf the supply, shove down the 
central tube to its proper position, and turn on the water again. 
A scaff net, small enough to easily enter the mouth of the jar, fixed to a handle 
several inches longer than the height of the jar, will be found a convenient tool for 
removing particles of foreign matter that will occasionally, in spite of every precaution, 
find its way among the eggs. 
MANIPULATING THE JAR WITH HEAVY EGGS. 
Practically there is little difference in handling any of the varieties of salmon and 
trout eggs, so little that no difference will be recognized in treating of their manage- 
ment. Such small differences of treatment of the eggs and fry as may be necessary 
will readily suggest themselves to the veriest tyro, and it is safe to assume them known 
to the expert. The term “ heavy eggs ” will be used as a general term to designate all 
species of salmon and trout eggs. 
When the eggs are received at the hatchery the first step is to ascertain their 
temperature. It is supposed of course that the hatchery has a fairly accurate ther- 
mometer. Remove the outer case and carefully introduce the thermometer into the 
egg package, allowing it to remain about twenty minutes, carefully withdraw it and 
observe the temperature. If there is a variation of more than four or five degrees 
between the temperature of the eggs and tlie water in which they are to be hatched, 
the package should be allowed to stand in the hatchery until the temperatures are 
equalized, or nearly so. If the packing material is frozen, frequent drenching with 
cold water, or even submerged in cold water 33° to 35°, is recommended. If the 
precaution is taken to gradually equalize the temperature, it will prevent the shock 
which would otherwise result to the eggs by a too sudden change of temperature. If 
the eggs are packed in shallow cotton or flannel bottom trays, covered with mosquito- 
netting and moss, they are easily washed into a jjau by a jet of water. Should they 
be packed in alternate layers of moss between netting, pick off the moss, take up 
the lower netting by the four corners, and pour the eggs into a pan of water. Any 
bits of moss or other foreign matter may be picked out with tweezers and the eggs 
thoroughly rinsed. The dead eggs are now picked out. This operation is one 
demanding some amount of skill. Dead eggs are white, but it is not safe to assume 
that every white egg is dead. In all cases give the egg the advantage of any doubt 
and remove none that are not known to be dead. If an egg be really dead, a few 
hours more will definitely settle the question. ^ 
The apparatus used in connection with the McDonald jar for picking over heavy 
eggs are a shallow square or oblong tin pan, filled nearly to the top with water, in 
which floats a tray with a wire-cloth bottom, a pair of ordinary tweezers, a small scaff- 
net, and several feathers from a turkey’s wing. The tray should be of some light wood, 
one inch less in length and breadth than the pan. A wire-cloth bottom of oblong mesh 
(one sixth of an inch by 1 inch) should be generally used for trout-hatching. Tweezers 
of wood are generally recommended above those of metal. The scaflf-net is conveniently 
made by bending a piece of copper wire for the frame and twisting the ends to form a 
handle. A good size is 4 by inches. Over this frame sew a piece of mosquito netting. 
