GRILSE 43 
its native element.” The exhaustive and most im- 
portant investigations of Dr. Noél Paton and his 
colleagues demonstrated most clearly the manner, 
inter alia, in which the great store of nourishment 
is used up in the development of the genitalia, and 
showed the corresponding loss in muscular tissue as 
this development proceeds. With the condition of 
satiety comes naturally the disposition to cease feed- 
ing, and with the cessation of feeding the ascent of 
fresh water commonly follows. 
So far we seem to be on perfectly safe ground, 
but I am inclined to think that the condition of 
satiety has been somewhat forced in the argument 
as to the result which it produces, viz., the ascent of 
fresh water. I admit that the normal condition of 
fish on entering fresh water is that of high nutrition, 
but let us inquire a little further into the argument 
that this high state of nutrition causes the salmon 
to leave the sea for the fresh water, or at any rate 
that this is the primary and dominating factor in 
the migration. Being in this highly fed up state, 
fish are able to fast for long periods ; and be it noted 
this is not peculiar to the salmon, but has been 
ascertained to be true, for instance, in the allied 
herring, whilst amongst higher animals the same 
peculiarity is reported as being true of seals. Why 
do they fast, and why does the salmon so fast only 
in fresh water? It has been said by way of explana- 
tion that, having attained an overplus of nutriment 
in its tissues, the salmon enters fresh water to rest, 
and that this may be regarded as natural, since in 
entering fresh water the salmon is in reality, as it 
