VIVIPAROUS FISH. 113 
to think that, a short time prior to the birth 
of the young, sea-water has access to this mar- 
supial sac, washes over the infant fish, the gills 
assume their normal action, and the regular 
systemic circle is established. Maturity at- 
tained, the umbilical attachment snaps, and the 
little fish, perfect in every detail of its organi- 
sation, 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 act- 
ing from the abdominal walls), I imagine, are in 
some way concerned in admitting the sea-water, 
and it appears to me a contrivance admirably 
adapted to effect such a purpose; but how im- 
pregnation takes place, | 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, 
Ican only conjecture that fecundation is accom- 
plished through the medium of the sea-water, 
admitted by the curiously-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 
VOL. I. ii 
