[5] ARTIFICIAL PROPAGATION OF FISH. 495 
mences about the end of November and is finished about Christmas. 
The spawning season for Southern Germany is during the months of 
November and December, and during these months the greater number 
of experiments in fecundation have been made by Mr. Detzem. J. 
Lamy* says that trout spawn from the 15th of December to the 30th of 
January, and Grand Forester Wagener of Detmold? reports that in 1853 
he succeeded in the artificial fecundation of the fish in question as late as 
March.t These facts prove sufficiently how necessary it is to have strict 
regard to the above-mentioned indications for recognizing the maturity 
of the spawn, as it is not safe to be exclusively guided by the indications 
as to the time when spawning takes place. 
The preservation of a suitable temperature during the process of arti- 
ficial fecundation is just as important as the perfect maturity of the 
eggs. Although we still lack complete and positive data relative to 
the extremes of temperature between which the fecundation of the dif- 
ferent kinds of fish can be more or less successfully accomplished, it 
my be considered as definitely settled that the success of the experi- 
ment dépends essentially on the temperature of the water, and that, 
owing to differences of temperature, it is often retarded or accelerated, 
and even in certain cases does not take place at all. Every piscicul- 
turist knows that fish never fail to spawn in certain waters presenting 
every favorable condition but that of the temperature of the water, but 
that not the slightest trace of young fry could be discovered, simply 
owing to the absence of a suitable temperature. 
According to the average period when fish spawn they are divided 
in “inter fish,”—the trout, salmon, burbot, &c.; “carly spring fish,”— 
the pike, &c.; ‘late spring fish,”—the perch, &c.; ‘summer fish,”—the 
tench, the carp, &c. From experiments made in France by M. de Qua- 
trefages it appears that the temperature most favorable for fecundation 
is, for fish spawning in winter from 4° to 6°, for early spring fish from 
S° to 10°, for late spring fish 14° to 16°, and for summer fish 20° to 25° 
Celsius. A difference of 4° to 5° in the above temperatures may thwart 
the success of fecundation. We will not attempt to disprove this asser- 
tion so far as the winter and early spring fish are concerned, although 
we have successfully fecundated trout eggs at a temperature of 4° to 
8°, As regards the other two classes of fish, we take the liberty to 
entertain doubts, whilst maintaining that the determining of the ex- 
remes of temperature should be made the subject of continued and care- 
ful observations. 
The necessity for executing the different manipulations of the pro- 
cess of fecundation as xapidly as possible is already explained by what 
we said above regarding the temperature of the water. But this rapid 
*J. Lamy: Eléments de pisciculture, Paris, 1855. 
tDr. Fraas: Ueber kiinstliche Fischerzeugung, p. 59. 
t The ordinance of 1669 fixes the spawning season of the trout from February 1st till 
the middle of May. 
