28 
DR. DAVY ON THE OVA OF THE SALMON, 
water of the same specific gravity as the last. It was hatched at the end of about 
forty-eight hours. The young fish was at first languid; now, on the fourth day, it 
is little altered; it is seen commonly lying on its side, and is restless only by fits 
and starts. 
Besides the experiments above detailed, 1 have made others, but differing so little 
in their results, that I do not think it necessary to describe them even in confirmation. 
VI. Concluding Remarhs. 
On the conclusions which may be drawn from the experiments as bearing on the 
subject under consideration I shall be very brief ; for the sake of order I shall advert 
to each section. 
From the experiments detailed in the first section, it would appear that the ova of 
the Salmon in an advanced stage can be exposed to the open air, if dry, but a short 
time, at ordinary temperatures, without loss of vitality; but for a considerable time, 
if the temperature be low and if the air be moist; the limit in the former case not 
having exceeded an hour, whilst in the latter it has exceeded many hours. 
From the experiments in the second section, it would appear that the vitality of the 
ova was as well preserved in air saturated with moisture, as it would have been 
had they been in water. 
From the expei’iments in the third section, it would appear that the ova might be 
included in ice without losing their vitality; but that if exposed to a temperature 
many degrees below the freezing-point, probably effecting their congelation, they 
were deprived of their vitality. 
From the experiments in the fourth section, it would appear that both the ova and 
the young fish were capable of bearing a temperature of about 80° or 82° in water for 
a moderate time with impunity, but not without loss of life at a higher temperature, 
any exceeding 84° or 85°. 
From the experiments in the fifth section, it would appear that a degree of saltness 
of water equal, or nearly equal, to that of sea-water is pretty speedily fatal both to the 
ovum of the Salmon and to the young fish ; that the same effect is produced on the 
young fish by brackish water of specific gravity 1016, but in a longer time; and that 
when the solution is so diluted as to be reduced to the specific gravity 1007, the 
advanced ovum may be hatched in it, and the life of the young fish may be sustained 
in it for many days, but with diminishing power. 
Finally, in reference to the distribution of species, do not many of the preceding 
results render it probable, in the instances of fish of the salmon-kind, and by analogy of 
other kinds, that it may be effected in the manner you have suggested in proposing the 
inquiry, viz. by means of impregnated ova conveyed by animals, whether birds or 
quadrupeds, adhering to some part of their body, such as their feathers or hair, feet 
or mouth, — by the latter provided the temperature do not exceed 84° or 85° ? And, 
during rain or snow, are we not warranted in concluding that an ovum may be taken 
