210 BULLETIN OF THE UNITED STATES FISH COMMISSION. I 
With a proper quantity of semi-buoyant eggs in the jar and the water turned on 1 
and regulated, the movement of the current establishes a regular boiling motion in | 
the mass of eggs, which brings each in succession to the surface. The intensity of | 
the boiling motion may be regulated at will without altering the quantity of water 1 
employed. By loosening the upper binding screw of the central stuffing box and j 
pushing the feed tube down until it almost comes in contact with the bottom of the | 
jar, the motion of the eggs is increased. If the jtir is working properly the dead eggs ) 
when brought to the surface do not go down to mix again with the live eggs, but | 
remain on top, forming a distinct layer. By pushing down the outlet tube a suitable j 
distance the dead eggs are lifted up by the escaping current and taken out, leaving a !| 
mass of clean, live eggs in the jar. The beveled edge of the binding screw permits | 
the swinging of the outlet tube over a large portion of the surface of the eggs. By I 
careful manipulation in this way it is possible to remove every dead egg without the ' 
loss of one live egg. 
The hatching is done on tables arranged for the work. The dimensions and ' 
arrangement of the tables are capable of indefinite modification. Working drawings ' 
of the tables used at the Central Station of the U. S. Fish Commission at Washington, ! 
D. C., are here given. (Plate 34.) j 
When the period of hatching has arrived among the semi-buoyant eggs, instead 
of allowing the water from the hatching-jars to pass directly into the sink, it is necessary j 
to co*hduct it into a receiving tank. j 
In the shad and whitefish hatching at Central Station, large rectangular glass i 
aquaria are used as receiving tanks, six or eight and sometimes ten jars discharging 
their fish into a common receiver. (Plate 35.) 
As receiving the fry of semi-buoyant eggs is practically the same with all forms of i 
hatching apparatus, it will not be further described. The handling of the heavy eggs | 
and their fry by this apparatus being entirely different from all others, it will be j 
mentioned under a separate paragraph. 
. I 
MANIPULATING THE JAR WITH SEMI-BUOYANT EGGS. ‘ 
The eggs are introduced into the jar by means of a shallow funnel (Fig. 2), as 
shown in the cut. The funnel is 
made of tin and is provided with - 
a rim of perforated tin or wire 
gauze. The jar, thoroughly clean, 
is filled with fresh water (never 
stale) and placed in a sink or pan 
to catch the overflow. The fun- 
nel is inserted in the jar so that 
the water will stand as high in 
the funnel throat as possible, and 
the eggs poured in from a pan or 
washed in from the transporta- 
tion trays by means of a jet of 
water. In this operation care 
must be used to have the eggs fall 
but a short distance and drop into the water. On no account suffer any fish scales or other I 
