NATIONAL FISHERY CONGRESS. 
359 
Now, suppose that all of these eggs were hatched, which would be a triumph of 
fish-culture beyond our wildest dreams, and that the 340,000,000,000 of larvm were 
liberated under the usual conditions; it is evident that from now on they must be 
beset by the same dangers and suffer the same losses as their fellows hatched under 
natural conditions. In the latter case it has been shown that it takes 200,000 eggs 
to produce one breeding fish. As we do not know just in what period of life this 
destruction of 199,999 out of every 200,000 takes place, we are forced to make a guess. 
Let us make one which can be proved to be liberal, and suppose that 75 per cent of it 
occurs while the embryo is developing in the egg, during a period at most of sis days, 
and only 25 per cent during the remainder of the three years. According to this, 
50.000 newly hatched larvrn would produce one mature fish of the average spawning 
age. Dividing the 340,000,000,000 by 50,000, we get 6,800,000 — a figure which, even 
under a series of hypothetical conditions ridiculously favorable, is below the desider- 
atum. The figures given are, of course, only approximate, and in one case a liberal 
guess, but they give some idea of the magnitude and difficulties of the undertaking. 
Let us now see what has actually been accomplished. Eepeated experiments have 
been conducted — both abroad and especially by the United States Fish Commission for 
several years past — in the hope of successfully propagating the mackerel. The eggs, 
like those of the cod and other marine fishes, are buoyant in water of the density of 
the open ocean, and the same apparatus has been used in this country as for the very 
successful cod hatching. The several forms of Chester and McDonald tidal boxes 
have been used with results which have been practically uniform for all. For the 
purpose of automatically changing and freshening the water, the principle of a tidal 
rise and fall induced by an intermittingly acting siphon is used. The eggs after ferti- 
lization are placed in a receptacle, either an open box the bottom of which is made of 
cheesecloth, or a cylindrical jar the open end of which is closed by cheesecloth, while 
the bottom is perforated by a hole which permits the ingress and egress of air. The 
cheesecloth end of either box or jar is supported on a frame fixed at a proper point 
(about 2 inches below the lowest point to which the water falls) in one of the tidal 
boxes. By this arrangement the water within the jar or box containing the eggs is made 
to partake of the same movement, and part of it is drained off and replaced by fresh 
water with each complete tidal oscillation, while the buoyant eggs float in a layer at 
the surface. They do not, however, long remain so, but during the course of develop- 
ment become — apparently because of the gradual absorption of the oil drop — gradu- 
ally heavier, and sink slowly toward the bottom. Here they lie in the midst of a mass 
of filth, which quickly collects, and, cut off from the light and air, sooner or later 
succumb. A few will usually hatch, but the larvae do not long survive. Attempts 
have beeu made to overcome this difficulty by increasing the density of the water, or 
by the use of shallow dishes in which the eggs are more directly exposed to the light 
and air. Both of these methods gave somewhat encouraging results, but the experi- 
ments could not be carried to a conclusion. Experiments with the ordinary tidal 
apparatus have been frequently repeated under varying conditions, but have almost 
always resulted in complete failure. 
The only important exception to this statement is to be found in the results reported 
during the past summer by Mr. Corliss, of the United States Fish Commission station 
at Gloucester. According to this statement, out of about 1,000,000 eggs handled 
450.000 were hatched. To explain the mortality it has been suggested that this result 
is due to imperfect fertilization, itself the outcome of some lack of vitality iu the egg 
