338 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
eggs; it is likewise sometimes caused bj r too sluggish a current in the troughs, too 
small a supply of feed water, lack of aeration, or from using the water over too 
many times. In many cases fungus will not occur if troughs and baskets are kept 
clean and the water is properly filtered. 
The troughs are designed to hold five baskets each, allowing for the necessary 
space between each for division plates, as well as the compartments at each end for 
receiving and aerating and discharging the flow of water. The aerators are of tin 
of the usual pattern and distribute the water well; at the opposite end of the trough 
is the usual arrangement of drainage plugs. The division plates are arranged accord- 
ing to the so-called Williamson system; that is, the first plate rests on the bottom of 
the trough with the water flowing over it, and, a short distance beyond, the second 
plate comes flush with the surface, but allows the flow to pass under it, the most 
approved method of conducting feed water through salmon eggs. Instead of rigid 
plates sliding in grooves at set intervals, division plates of light galvanized sheet 
iron, thickly asphalted, are used; these are half an inch longer than the width of the 
trough and are snapped or sprung in at any point desired. A drop of about 1 V 
inches is given each trough, and the water is used four times before discharging into 
the waste trough. 
The waste trough is a continuous wooden box, built of heavy redwood boards, 
which passes under the lower, or fourth, trough of each set and carries off the entire 
waste of the hatching-house; it passes around the south wall and part of the east wall 
and thence into the reservoir, where it discharges. 
The baskets are 21 inches long, 15 inches wide, and 6£ inches deep, inside meas- 
urement., made of galvanized-wire netting secured to a single wooden frame. The 
