208 U. S. BUREAU OF FISHERIES. 
remain undisturbed until the curvature of the tail is visible to the unaided eye. 
The accumulation of a moderate coating of sediment which readily washes off is not 
injurious. In a few instances it has become necessary to handle the eggs during the 
tender stage to arrest the spread of fungus, but where the water supply is reasonably - 
well adapted to fish-cultural purposes such a course is rarely if ever necessary. 
REMOVAL OF DEAD EGGS BY THE USE OF SALT SOLUTION. 
Among the most noteworthy advances in the fish-cultural methods during the last 
few years has been the use of salt as an aid in the removal of dead eggs. The develop- 
ment of this process has extended over a period of several years, but it is more during 
the last year or so through the efforts of L. E. Baldridge, of the Yes Bay station, that it 
has reached a high degree of efficiency. 
Compared with the time-honored process of picking by hand, there are marked 
advantages in using the salt solution, and chief among these is the great saving of labor. 
It is estimated that if the eggs happen to be of not more than mediocre quality it 
would take at least 20 pickers to remove as many dead eggs as could two men using the 
salt solution. Moreover, the operation is much more thoroughly performed in the 
latter process than is possible in picking by hand. 
Another advantage of using the solution is that it is possible thoroughly to clean 
the eggs. This greatly reduces any loss through contamination and infection resulting 
from the decomposition and fungous growths which inevitably follow the long-con- 
tinued presence of dead eggs that in the hand-picking method frequently escape 
attention. Even when utmost care is taken to pick out all dead eggs, fungoused 
masses will occasionally appear. This condition is rarely observed when the salt 
solution has been used, and it undoubtedly means that in the aggregate many eggs 
are saved. Still another point in favor of the solution, it is generally believed, is that 
it acts as a tonic or stimulant to the good eggs while at the same time as a deterrent to 
the growth of fungus. Again, in picking by hand there is apt to be loss by move- 
ment of the eggs during delicate stages of development; and the oft-repeated insertion 
of egg tweezers, which are bound to touch other eggs, undoubtedly at times results 
in injury. 
Recent experience has demonstrated that the solution may be applied effectively 
to eggs freshly taken as well as those in more advanced stages of development. 
The principle of the salt bath is simply that the specific gravity of the good eggs is 
greater than that of the bad eggs, hence upon being placed in the salt solution the 
good eggs sink and the bad remain afloat and are easily removed. It is vitally essen- 
tial to the success of the undertaking that the solution be of the proper strength, and 
it is for this reason that the beginner is apt to become discouraged. If the solution is 
too weak all the eggs, both good and bad, will sink, while if it is too strong all will 
remain afloat. The margin of the proper density is so narrow that in the operation it 
is necessary every few minutes to strengthen the solution by adding more salt or brine, 
otherwise the small amount of fresh water which adheres to a basket of eggs as it is 
lifted from the hatching trough into the solution will affect unfavorably the results 
when treating succeeding baskets. Experience and careful observation, however, 
will soon make it possible for the operator accurately to judge when to add a bit of the 
stock solution. It is a convenience, of course, to have a salinometer at hand when 
preparing the solution. _Itis commonly the practice as an aid in preparing the solution 
to test it occasionally with a few eggs. 
Highly successful results in using the solution with red salmon eggs have been 
attained at the Yes Bay station, and a detailed description is accordingly given of the 
methods pursued at that place. 
The chief item of equipment consists of a water-tight wooden tank 4 feet long, 24 feet 
wide, and 10 inches deep for holding the solution in which the eggs are immersed. 
Before each basket is immersed it is necessary that the surface of the solution be 
perfectly quiet, for any ripple or current will tend to disturb the buoyant effect of the 
solution upon the eggs. ‘therefore it was found of great convenience last winter to 
use a floating frame made of half-inch material 6 inches wide fastened together verti- 
cally and at right angles, thus forming open squares about 6 inches either way. After 
each basket of eggs 1s lifted from the salt bath this frame is placed in the solution to 
stop all motion of the water, being pushed down until it is almost submerged and held 
firmly against the side of the tank fora few seconds. Upon being carefully withdrawn 
the solution is quiet and the next basket of eggs may be immersed without further 
delay. 
Another piece of equipment is a feather fan with which gently to push the floating 
dead eggs away from over the submerged basket into which the good eggs have settled. 
Unless the dead eggs are quickly moved they too willsink, A feather fan made by 
