THE FEEDING OF SALMON 123 
course freely admit ; but, as suggested in the chapter 
on grilse, it is possible to regard the first seaward 
migration as a movement to the salmon’s original 
habitat, 2.e., the habitat from which our salmon as we 
now know it, along with its near allies, took its origin 
inremote times. The shad isa sea fish which visits 
our rivers to spawn. The sparling or smelt must be 
similarly regarded, and is more nearly related to the 
salmon than the shad. Attempts at producing 
fertile salmon without allowing them to visit the 
sea easily fail, and when successful, result in 
degenerate creatures which do not support the idea 
that they represent the prototypes of fish from 
which the evolution of our salmon has sprung. The 
vigorous growth and development in the sea, on the 
other hand, and the fact that the salmon spends 
most of its time in this element, along with the 
arguments already cited in the chapter on grilse, 
from the systematic study of the salmon family, in- 
cline me to the view that the sea was the original 
habitat of Salmo salar, as it undoubtedly was of 
most of the salmon family. 
If this is so, there is nothing forced in the belief 
that the long migration fish, continuing in the sea 
as it must do long after its tissues have become fully 
nourished, and as the study of the scales certainly 
indicates, is simply living in itsnatural habitat. At 
the same time, I do not consider that the nisus 
generativus prompts the spring fish to enter fresh 
water. The late running fish which has already 
developed its genitalia in the sea may be said to 
visit the river for the purpose of spawning, but the 
