104 FISH CULTURAL ASSOCIATION. 
the course of their wanderings, while eels planted in such isola- 
ted bodies of water thrive and grow rapidly but never increase 
in numbers. Another still more convincing argument is the 
fact that in lakes which formerly contained many eels, but 
which, by the erection of impassable weirs, have been cut off 
from the sea, the supply of eels has diminished, and after a time 
only scattering individuals, old and of great size are taken in 
them. An instance of this sort occurred in Lake Miiskendorf, 
in West Prussia. If an instance of the reproduction of the eel 
in fresh water could be found, such occurrences as these would 
be quite inexplicable. 
In the upper stretches of long rivers, the migration of the eels 
begins in April or May, in their lower stretches and shorter 
streams, later in the season. In all running waters the eel fish- 
ery depends upon the downward migrations; the eels press up 
the streams with occasional halts, remaining here and there for 
short periods, but always make their way above. They appear 
to make the most progress during dark nights when the water 
is troubled and stormy, for at this time they are captured in the 
greatest numbers. It is probable that after the eels have once 
returned to the sea, and there deposit their spawn, they never 
can return into fresh water but remain there to die. A great 
migration of grown eels in spring or summer has never been 
reported, and it appears certain that all the female eels which 
have once found their way to the sea are lost to the fisherman. 
In No. 8 of the German Fischeret Zeitung for 1878, Dr. Schock 
published certain statements sent to him by Dr. Jacoby. It is 
remarked in this paper, among other things, that after the depo- 
sition of the spawn, the female eel dies a physiological death, 
and that occasionally the sea in the neighborhood of the mouths 
of rivers has been found covered with dead eels whose ovaries 
were empty. When, where, and by whom this observation was 
made, and who pronounced upon the empty ovaries in these 
dead fish is unfortunately not mentioned. 
A great number of the eels remain in inland waters while 
others proceed to the sea, either because their eggs are at this 
time not sufficiently ripe, or perhaps because they are sterile. It 
would seem probable that the increase in the size of the eggs in 
