250 DR DAVY ON THE SALMONIDZ. 
appeared in the lower, all but one egg were hatched in the upper, and that one 
proved to be dead. On the 20th, and not till then, another egg, the second, was 
hatched in the pan. On the 22d, it is noted that many more were hatched dur- 
ing the twenty-four hours, the temperature of the water being about 52°. From 
the 22d to the 31st, the hatching process continued, a few young fish appearing 
daily. Those last produced, it was observed, were smaller and feebler than the 
first, and died in larger proportion. 
It is worthy of note—such was the remark made at the time—how, under the 
same circumstances, as in the water-glasses, or under slightly different circum- 
stances, as in the earthenware vessel on the floor, ova from the same fish, im- 
pregnated with the same milt, at the same time, differ so much as to the time of 
being hatched, the size of the fcetal fish, and their vitality both before and after 
exclusion, some embryos dying in the egg, some in an advanced stage in the act of 
extricating themselves, other young fish at intervals of hours or days. 
Now, what was witnessed in these experiments, it can hardly be doubted oc- 
curs in the natural process of hatching, in which the circumstances commonly 
must be very much more varied, and the results, it may be presumed, equally so, 
and not without advantage as regards the preservation of the species. 
5. Of the circumstances and agencies likely to exercise an influence on the Young Fish. 
In the paper before referred to, ‘‘ Observations on the Charr,” a section was 
given to the subject above named. The inquiry was, as it appeared to me, an 
interesting one; and it was my intention to prosecute it farther, but hitherto 
I have done little for want of opportunity, and that is comprised in two trials, 
one on keeping the young fish excluded from light; the other on placing them in 
a very small quantity of water, barely sufficient to cover them. 
The first trial was commenced on the 31st of January. On that day, one of 
the water-elasses, with its brood of young charr, was placed in a dark cupboard, 
from which light was entirely excluded. Here they were kept till the Ist of 
April; during which time the vessel was taken out only once daily, for the pur- 
pose of changing the water and giving food, which occupied no more than a minute 
or two. Now, comparing them with the brood in the other water-glass, which 
had been daily exposed to the light, I could perceive no well-marked difference 
in the appearance of the fish as to form, colour, progress of growth, or activity. 
The only difference noticeable was, that those kept in the dark were much shyer 
than those exposed to light, which was indicated, on their being brought to 
light, by their endeavouring to hide themselves; this they did by thrusting the 
head under the gravel. 
The other trial was made on the 13th and 17th February, with healthy young 
charr, hatched between the 8th and 10th January, and on the 10th March on a 
young salmon hatched about the 26th February. On the first-mentioned day a 
