No. 465.] STUDIES OF MYXINOIDS. 639 
them was lying almost straight. Both were put into the small 
aquarium with running water at a temperature of 22? C.; they 
swam freely for a few minutes, then settled down against the 
outflow pipe, having regained their normal habit. This was 
between half-past twelve and one o’clock. It was an exceed- 
ingly warm day, the thermometer standing at 89°F. in the 
shade, and the aquarium was so placed that the afternoon sun 
streamed directly upon it. About five o’clock I noticed that 
the two hagfish were very languid and stretched almost straight. 
On testing the water I found that it had risen to 29° C. Sud- 
denly, the hagfish, without anything being done to disturb them, 
began to swim in a very violent, jerky way, and to throw out 
strings of slime, which is never done except when they are 
irritated. They would swim and stop intermittently, always 
lying at full length when at rest, and swimming so irregularly 
and violently as to injure themselves. When put into cooler 
water, 22? C., they immediately settled down quietly, half 
stretched out. I placed them in a small wooden tank in the 
cellar, by the large tank, in order to keep them separate from 
the other fish for a while, and note what after-effects there 
might be. The next morning one of them had escaped to the 
floor, together with two from the large tank. Of these three, 
two were entirely normal, and one was dead, in all probability 
the one that had been exposed to the heat the day before. The 
other hagfish grew steadily more languid, and died at noon the 
next day, two days after the experiment. Both fish were in a 
normal condition when the experiment began. It was positively 
the heat from which they suffered, and not the actinic rays, 
because they had been exposed to brilliant sunshine every after- 
noon for a month, and no ill effects had followed. The day 
they were affected was the first day there had been a marked 
rise in temperature. 
Taken as a whole the hagfish do not lead an active life. 
When thoroughly aroused and on the alert, they swim at a very 
high speed, with a graceful, serpentine motion, but for the most 
part, they lie placid, perhaps motionless, perhaps lazily moving 
their heads from side to side. They are more active by night 
than by day. In the daytime more than once I found some of 
