198 FISH—CULTURAL ASSOCIATION. 
instance, that shocks given to fish eggs during the time that 
they are in process of incubation, will often produce monstros- 
ities, and if very violent will produce death. Shocks may be 
exerted as the result of natural causes, or may be brought about 
in the course of the application of.artificial methods in the incu- 
bation of fish ova. The ordinary mode of formation of any fish 
embryos is around a globular vitellus. There is a dome-shaped 
cap of plastic material formed over the yelk in which nuclear 
matter is imbedded immediately after fertilization. Segmenta- 
tion proceeds step by step, and in the course of this process 
shocks may produce aberration of development. The germinal 
matter at first covers, or is partially scattered through the vitellus 
and connected with the surface, migrating toward that surface and 
to one point so as to form a discoidal germinal mass at one side 
of the egg. That, of course, is not the first step in development. 
Now it is easy to understand that the shocks would impair the 
delicate processes of development going on within, especially 
when we remember that during this time the nuclear matter is 
arranged in a certain peculiar way, and that as cleavage pro- 
ceeds, this nuclear body elongates and throws out rays through 
the enveloping protoplasmic matter. If at this stage of devel- 
opment I should shake the eggs violently, a second embryonic 
axis may be formed which soon fuses with the axis of the origi- 
nally formed embryo, and the result would be a double-headed 
fish. Thus you can readily see that certain forces tend to dimin- 
ish the number of normally developed embryos, malforming 
them and producing irregularities which cannot become adult 
or perfect fishes like the parents. 
I have only mentioned some of the forces which are opera- 
tive in diminishing the chances of survival of young fishes, but 
I trust that enough has been said to indicate to some extent, 
the nature of the ploblem still to be solved by those who are 
interested in the breeding, protection and multiplication of food 
fishes. 
The first and most important principle which I would espe- 
cially commend to the thoughtful attention of the Association is 
the general law already hinted at, namely: that just in propor- 
tion as the individuals of a species are prolific in respect to the 
