408 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
certain point; then, I think, the membrane enfolding the ova, that have by this time assumed a fish- 
like type, takes on the character and functions of a placental membrane, and the young fish are sup- 
plied by an umbilical cord, just as in the case of a foetal mammal. But a third change takes place. 
There can be no doubt that the young fish I cut out, and that swam away, had breathed before 
they were freed from their mother; hence I am led to think that, a short time prior to the birth of 
the young, sea-water has access to this marsupial sac, washes over the infant fish, the gills assume 
their normal action, and the regular systemic circle is established. Maturity attained, the umbilical 
attachment snaps, and the little fish, perfect in every detail of its organization, is launched into the 
deep to brave its many perils and shift for itself. The strong transverse muscles attached to the 
powerful sphincter (constituting the genital opening acting from the abdominal walls), I imagine are 
in some way concerned in admitting the sea-water, and it appears a contrivance admirably adapted to 
effect such a purpose; but hpw impregnation takes place I may at once honestly confess — I do not 
know.* 
The male is much like the female, but more slim, and the milt just like that of other fish. I 
can only conjecture that fecundation is accomplished through the medium of the sea-water, admitted 
by the curiously cell-contrived floodgate of the female, carrying in the milt-germs and washing them 
over the ova. 
The actual period of utero-gestation I am by no means sure about, but I am inclined to think 
they breed twice in the year. It : s worthy of remark that the young mature fish are very large, 
when compared with the size of the mother. In a female fish 11 inches in length, the young were 3 
inches long, the adult fish 4£ inches high, the young an inch. 
But now for the most important feature in the history of these fish — that of bringing into the 
world their young alive, self-dependent, and self-supporting, as perfect in their minutest organization 
as the parent fish that gives them birth. The generative apparatus of the female fish when in a 
gravid state may be defined as a large bag or sac. Ramifying over its surface may be seen a most 
complicated and strangely beautiful vascular arrangement — a network of vessels, the use of which is 
clearly to convey the life-giving fluid to the infant fish, and carry it back again, after having served 
its destined purpose, to be revivified for future use. The way the sac is, as it were, folded, and the 
different compartments made for the accommodation of embryonic fish, is most singular, and very 
difficult to describe clearly. 
The best illustration I can think of is an orange. You must imagine the orange divided into 
its regular number of little wedged-shaped pieces, and each to represent a fish ; that the rind of the 
orange is a delicate membrane, having a globular shape, and easily compressed or folded. You now 
desire to fit the pieces together again in the original orange-shape, but you must begin on the outside 
of the globular membrane, pressing in with each section a fold of the membrane (remember that 
each represents a fish) ; when each piece is in its place, you will still have the sac in its rounded form, 
but the rind or membrane has been folded in with different pieces. If I have made myself under- 
stood, it will be seen that there must be a double fold of membrane for each portion of orange. This 
is exactly the way the fish are packed in this novel placenta] sac. If it were practicable to remove 
each fish from its space, and the sac retain its normal shape, there would be twelve or fourteen open- 
ings (depending upon the number of young fish), the wall of each division being a double fold of 
membrane, the double edges wrapping or, as it were, folding over the fish. Now make a hole in the 
end of this folded bag, and blow it full of air, and you get at once the globe-shaped membranous sac I 
have likened to an orange. 
The fish are always arranged to economize space; when the head of a young fish points to the 
head of its mother, the next to it is reversed, and looks towards the tail. I am quite convinced that 
the young fish are packed away by doubling or folding the sac in the same way I have endeavored to 
describe. I have again and again dissected out this ovarian bag, filled with fish in various stages of 
development, and floating it in salt water, have, with a fine pointed needle, opened the edges of the 
double membranous divisions that enwrap the fish (the amount overlapping is of course greater when 
the fish is in its earlier stages of development). On separating the edges of the sac, out the little fishes 
pop. I have obtained them in all stages of their growth, but sometimes (and this not once or twice, 
but often) have set free the young fish from its dead mother. Thus prematurely cut loose from its 
membranous prison, the infant captive, reveling in its newly-acquired liberty, swam about in the 
salt water, active, brisk, and jolly, in every particular, as well able to take care and provide for itself 
* It is perhaps needless to state that the above paragraph is far from stating what does take place. 
