6 XJ. S. BUREAU OF FISHERIES. 



and the process repeated until all good eggs have been secured. If, 

 as is frequently the case, a considerable number of white eggs appear 

 when nearly all the ripe eggs have been emitted, the effort should 

 cease. 



In the dry process of impregnation, which is now generally con- 

 ceded to be superior to the wet process of fertilization, the pan in 

 which the eggs are taken is dampened by dipping it in water before 

 stripping begins. After one or two females have been manipulated 

 the milt from one or two males is added to the eggs, this being done 

 by grasping the fish between the thumb and fingers 2 or 3 inches 

 forward of the vent and moving the fingers toward the opening. 

 The milt comes in a stream, an average fish yielding about a tea- 

 spoonful. If ripe males are scarce, the fish is laid aside, as a 

 considerable amount of additional milt may be secured from it a 

 few minutes later in case it is needed. 



When the pan is one-third to one-half full of spawn and milt, the 

 spawn taker stirs the eggs gently to incorporate them thoroughly 

 with the milt, using for the purpose the tail of a fish from which 

 the slime has been carefully removed. The pan is then partly 

 filled with water and the mass stirred again very gently. After 

 standing two or three minutes the water is poured off and fresh 

 w^ater added, this operation being repeated until the water flows off 

 clear. The eggs are then poured into a keg or can that has pre- 

 viously been filled with water and the mass again stirred very 

 gently. It is necessary to change the water on the eggs at least once 

 an hour, oftener if the weather is warm, and they should be stirred 

 gently to the bottom of the keg every 30 minutes until placed in 

 running water in the hatchery. 



After finishing his work the spawn taker delivers the eggs to the 

 man in charge of field operations, who cares for them until the ar- 

 rival of the collecting steamer, when they are taken on board and 

 transported to the hatchery, some two to five hours having elapsed 

 since they were taken. At the station the eggs are kept in the kegs 

 in which they were placed by the spawn taker, and in the mean- 

 time the water is changed once every hour until the next morning, 

 the mass being stirred to the very bottom whenever a change is made. 

 In this way the eggs are hardened with less injury than would re- 

 sult if they were immediately placed in the jars. 



Formerly, in shipping eggs from distant field stations, they were 

 kept in running water in kegs, under the care of a watchman, but 

 experience has demonstrated that it is much better to ship them in 

 cases on trays. After being in water from 8 to 10 hours whitefish 

 ova may be safely placed two or three layers deep on trays and 

 shipped to an indefinite distance. If the air temperature is as 

 high as 55 to 60° F., the case must be supplied with ice; if it is 

 below 32° care must be taken to prevent freezing. 



The field shipping cases are usually constructed of lumber three- 

 fourths of an inch thick and of sufficient depth to hold 20 trays. 

 The bottom tray and the top tray are not used for eggs. Cleats at 

 the four inner corners hold the trays about 1^ inches from the sides 

 of the case. 



A tray hoard is a convenience in spreading eggs on the trays. 

 This consists of a smooth board some 4 inches greater in length and 

 width than the egg trays, with a raised rim one-half inch high and 



