472 AMERICAN FISHES. 
which immures the Trout in their homes in the hill country as closely as 
would a mountain wall. Difficult Run; a few miles above Washington, is 
a natural Trout stream, and the species occurs in other streams near Balti- 
more and Washington. 
When Trout have no access to the sea they still contrive to avoid a 
change of temperature with the seasons. In midsummer they lie in the 
bottoms of lakes cooled by springs, in the channels of streams, or in deep 
pools, lurking behind rocks and among roots. In spring and early sum- 
mer they feed industriously among the rapids. At the approach of cold. 
weather in autumn they hasten to the clear shallow water near the heads 
of the streamlets. It is at this time that they deposit their eggs in little 
nests in the gravel which the mother-fish have shaped with careful in- 
dustry, fanning out the finer particles with their tails, and carrying the 
large ones in their mouths. After the eggs are laid, the parent fish covers 
them with gravel, and proceeds to excavate another nest. The same nests 
are said to be revisited by the schools year after year. 
The spawning season begins in New England in October, continuing 
from three to six months, and during this period the fish should be pro- 
tected by stringent laws. Mr. Livingston Stone observed that in his 
ponds at Charlestown, N. H., spawning began October 12 and ended 
early in December ; at Seth Green’s establishment, near Rochester, N. Y., 
it began on the same day, and continued until March. At the former 
station spring water, with a uniform temperature of 47°, was in use, 
while at Caledonia the eggs were kept in brook water, which is colder in 
midwinter, retarding development. 
Trout eggs are usually three-sixteenths of an inch in diameter, although 
varying greatly, and are colorless, red, or orange-hued. The quantity 
yielded by a fish is in direct proportion to its size, the average being from 
four to six hundred. Mr. Stone took sixty from a half-ounce fish, and 
eighteen hundred from one which weighed a pound. The eggs having 
been laid, their time of development depends strictly on the temperature 
of the water. According to Mr. Ainsworth, they will hatch in one hun- 
dred and sixty-five days with the mercury at 37°, one hundred and three 
at 41°, eighty-one at 44°, fifty-six at 48°, forty-seven at 50°, thirty-two 
at 54°, &c. Seth Green’s rule is that at 50° they hatch in fifty days, 
every degree warmer or colder making a difference of five days. After 
the eggs are hatched the yolk sac is absorbed in from thirty to eighty 
