78 
THE CALIFORNIAN SALMON. 
to deposit their spawn, as happens in some of the American 
rivers, that they are never known to return to the sea. 
When the period of spawning approaches, the male salmon 
has a cartilaginous excrescence on the point of his under 
jaw, which, like the antlers of the deer, grows with great 
rapidity at this time. This protuberance is common to 
nearly all the varieties of salmon and trout, but is 
developed to a much greater extent in the salmon, and 
especially in the salmo quinnat^ or Californian salmon, 
found on the west coast of North America. The horny 
excrescence turns upward, and is sometimes several inches 
in length ; in some cases a corresponding hollow is formed 
in the upper jaw, the protuberance being occasionally 
developed to such an extent as to prevent the fish from 
feeding, which consequently dies of starvation. In the 
salmo salar it is less prominent, and still less so in the 
trout, and it gets partially absorbed after the spawning 
season, to re-appear again when the next spawning time 
returns. 
The ova that have been deposited in the gravel of the 
river bed, or those that escape the dangers to which they 
are exposed, from their many natural enemies, remain for a 
period ranging from 50 to 130 days, before hatching. The 
period of incubation varies, according to the temperature 
of the water. It has been found that salmon or trout 
ova will hatch in about 50 days, in water at a tem- 
perature of 50 deg., every degree above or below this 
temperature, shortens or lengthens the time of incubation 
by five days. They would eventually hatch out, even if the 
water of the stream were at freezing point, but if once 
subjected to a temperature much below 32 deg., it is said 
that their vitality is destroyed. 
The ova of the salmo salar, when from a ripe fish in 
the best condition, are almost exactly a quarter of an inch 
