330 DR DAVY’S OBSERVATIONS ON THE CHARR. 
in water ; they were kept part of the time in the open air, and part of it in the room 
of equable temperature: each fish had been hatched about six weeks. The one 
in water, with oxygen, put in on the 28th of January, was very active till about 
the middle of February ; about the 24th of that month it began to appear lan- 
euid, and it was more so on the 26th, when it was taken out and transferred to a 
vessel fully exposed to the air, and the water in which was changed daily. 
Though it lived till the 18th of March it did not recover its activity. Its growth 
whilst under oxygen was much the same as if it had been kept in water exposed 
to the air and changed daily. The oxygen used was not tested for carbonic acid; 
by the taper-test its purity did not appear to be impaired. The trial with com- 
mon air was commenced on the 7th of February; on the 13th, the young fish was 
found dead. As there was a small spot of stagnant blood in the vitelline mem- 
brane, its death might be owing to disease unconnected with the peculiarity of 
circumstances in which it was placed. On the 28th of March I repeated the ex- 
periment with a young fish which was vigorous and active. Taken out on the 
4th of April, its activity seemed unimpaired ; it fed greedily. This fish had been 
hatched about seven weeks. 
The only other trials I have made have been on the effects of temperature,— 
an influence that this fish appears to be peculiarly sensitive of, as indicated in all 
its habits, and in the circumstance that it is only found in those lakes in which, 
in consequence of their great depth, it can find a retreat in summer and winter in 
water of about 40° Fahr. On the 28th of March I transferred into water, of the 
temperature of 83°, a young charr that had been hatched not quite seven weeks. 
It rushed about for a second or two, then turned on its back and rose almost in- 
animate to the surface. The heart and gill-covers being still in motion, it was 
instantly put back to the water from which it had been taken of 52’. It made 
one or two efforts as if reviving, swimming for a few seconds in a natural posi- 
tion ; but in less than a minute it was dead, the heart having ceased to act: thus, 
compared with the effects of a solution of common salt, offering a remarkable con- 
trast. On the 29th of the same month, a young charr of about the same age as 
the preceding was put into water of 75°: it immediately became very restless ; 
its gill-covers moving rapidly. After a quarter of an hour, when the temperature 
of the water had fallen to 70°, it lay still at the bottom and not apparently dis- 
tressed, except that the movement of the gill-covers and the action of the heart 
were unduly quick. In an hour and a-half, when the water was 60°, it was still 
at rest: some hours later, when the water was 54, it seemed well; and, on the 
following day, put into fresh water, it appeared as active as before. 
I have now to conclude. This I shall do without entering on the embryology 
of the charr,—a vast subject, which, in the instance of one of the family of the 

