358 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



ston experiments. The hatching room was at first equipped with 224 

 of these incubators, known as the Clark hatching box, together with 

 their appropriate accessories. The hatching box itself' was a great im- 



provement over the system of gravel troughs formerly employed in fish 

 hatching, and the method and character of its work are even now un- 

 surpassed for incubating some of the larger eggs of the salmonoid 

 species. The invention, however, involved the same principle of con- 

 struction and operation that was embodied in two or three other similar 

 inventions which appeared about the same time. In each the method 

 of procedure consists in spreading the eggs in layers on wire trays, and 

 causing the water to flow through them. In some incubators of this 

 type the mechanical construction forces the water upward instead of 

 downward, but whatever the direction of the water the results in all are 

 substantially the same, since the eggs remain motionless. 



From the site of the hatchery and its immediate vicinity innumerable 

 springs send forth an inexhaustible supply of pure water. In the ag- 

 gregate they furnish about 700 gallons per minute. From the head of 

 this spring area to where the hatchery is situated occurs a natural slope 



tion room, w here they remain in perfect condition in pure running water until placed 

 in the waters designed for them. 



M is a shallow trough supplied with water drawn from the main tank, being the 

 same temperature of thai in which i ho eggs are hatched. 



During the first Jew weeks of their incubation many imperfect and dead eggs are 

 found, and for the purpose of removing them from the good ones the screens upon 

 which they li«' are removed from the hatching boxes to the shallow trough of running 

 water and picked out in the usual way with forceps, as sliowu by the figures in the 

 illustration. 



