4 DR DAVY ON THE IMPREGNATION OF 
vided with folds,—a somewhat valvular structure, that reminds one of the mouth 
of the common gall-duct in man,—allowing a free passage to a probe downwards, 
but not in the opposite direction, and being amply provided with mucous fol- 
licles, forming a provisional mucous duct, the better adapted to the descent of 
the ova.* In the male, the testes terminate in a common duct, slightly promi- 
nent within the verge of the anus,—the projection so small as hardly to deserve 
the name even of papilla, very much smaller than that of the female, and neither 
vascular, so far as I could ascertain, except in the ordinary manner, nor provided 
with any follicles, such as usually belong to the part destined for the purpose 
supposed. 
Further, if attention be given to the manner in which the male and female 
fish behave during the spawning time, I think we shall have confirmation that 
there is no act of intromission,—which indeed, anatomically considered, it may 
be presumed there cannot be,—but also that there is no attempt made favour- 
ing the notion that the spermatic fluid is injected (as would be necessary for the 
impregnation of the ova) into the cavity of the abdomen of the female. That 
the fish in the act of spawning sometimes come in contact, pressing against each 
other, and thereby aiding the expulsion of the ova and milt, cannot, I think, be 
doubted. By many observant fishermen, poachers addicted to the taking of the 
fish at the time of their spawning, I have been assured of the fact from their own 
observations; but this is very different from the act of copulation as performed 
in other classes of animals in which impregnation is effected before the expulsion 
of the ova; but though so dissimilar, perfectly suitable to the end required, and 
quite in accordance, as we have proof in the artificial process, with the neces- 
sary requirements. 
It is an axiom that nature does nothing in vain; it is not less true that na- 
ture is perfect in her works, as regards the adaptation of means to ends. In no 
part of the animal economy is this more strongly and happily illustrated than in 
the generative system of organs, diversiform and varied as they are in the several 
classes of animals. Consistently, then, were the mode of impregnation that 
which has been asserted, we may be sure that an organization,—an apparatus 
would have been provided suitable to it. Also, as I think consistently with the 
hypothesis, we might expect occasionally to find ova in the cavity of the abdo- 
men, bearing marks, if they had been impregnated there, of incipient develop- 
ment, according to the analogy of extra uterine foetal growth sometimes witnessed 
in the Mammalia; but none have been described, that I am aware of, as ever 
observed. In spent fish, that is, those which have spawned, in the instance both 
* The closure of this aperture, after the exclusion of the ova, from such observations as I have 
made, appears to take place slowly, requiring many weeks for its accomplishment, and when effected, 
by so delicate a medium as to be easily ruptured. To be properly examined, the fish should, after being 
opened, be placed under water, and the blow-pipe be used before the probe. 
