REPORT OF COMMISSIONER OF FISH AND FISHERIES. XCI 
considerable layer of glairy, viscid substance, u which becomes soft and 
stringy upon contact witli the water, but hardens later into a firm sub- 
stance, which finally cements the ova firmly to whatever they may be 
brought into contact with.” The period of incubation lasted six days. 
The embryo when first hatched measures barely half an inch in length, 
and is provided with a large yolk sac. After a few days the latter is 
absorbed, and the young fish, then measuring nearly three-fourths of 
an inch long, must begin to forage for itself. Owing to its small mouth 
at this time, the food taken must be microscopic in character, and prob- 
ably consists of rhizopods, unicellular algae, infusoria, the minute larvae 
of insects and worms, the very smallest crustaceans, etc. Specimens 
1 to 1J inches long were provided with minute teeth on the pharyngeal 
floor and had been feeding upon certain groups of the entomostraca, 
while amphipod and isopod crustaceans formed the principal food of 
those having a length of 5 inches to 2 feet. The adult fish, as may be 
inferred from the conformation of the head and mouth, are essentially 
scavengers and bottom feeders, and their diet probably includes a wide 
range of the more stationary forms of aquatic invertebrates. In the 
majority of the roe fishes brought to the butchering floats the spawn 
is nearly mature, being, however, still hard and firm and in the con- 
dition most highly prized by the packers of caviare. The variety best 
suited to the purposes of the fish-culturist is that which is just mature 
and ready to be artificially fertilized. According to Prof. Ryder, 
Most of the egg s of the ripe roe have ruptured their follicles, and as soon as the abdo- 
men is cut open the ova escape in great quantities, to the amount of several gallons in 
the case of a large fish. The quantity of eggs yielded by a single fish may, in fact, 
vary between 5 and 15 gallons. * * * It may be assumed that the average is 
about 10 gallons. * * * The eggs measure 2.6 millimeters in diameter, or a lit- 
tle less than one-ninth of an inch. At this rate we should find about about 168,000 
eggs to the gallon, and a total of from 800,000 to 2,400,000, according to the amount 
of roe in a single fish, estimated in gallons. 
The eggs, when in exactly the right condition, are globular, nearly a ninth of 
an inch through, and vary in color from a very light brown to a very dark brown. 
At one side a darker round disk may be observed, the diameter of which is about 
one-fourth of the circumference of the egg. This disk is also quite as visible in 
ova which have not yet escaped from the follicles in which they were developed 
as in the “hard roe,” for example. The darker discoidal area is the germinal area of 
the egg of the sturgeon, and is the point where development first manifests itself 
to the unaided eye, through certain changes in its shape. The eggs of the kind 
above described should retain their globular form, like so many shot, and should 
show no sign of adhering to each other. If the round area at one side of the eggs 
should appear distorted or broken it is also a sign that the eggs are probably worth- 
less for fertilization. Eggs with a round disk, if they flow freely from a slight cut 
through the walls of the abdomen of the recently caught living fish, may be fertil- 
ized without difficulty, provided a ripe male is at hand. Eggs which do not answer 
the requirements given in this paragraph it is not worth while to waste time over. 
The reproductive organs of the males are not nearly as large as the 
ovaries of the females, and probably never much exceed 10 to 15 pounds 
in weight. If removed from the living male when mature, and cut open, 
