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greater energy and this shows itself on the scale as a broader ring 
all round a narrow, and sometimes very narrow, ring which repre¬ 
sents the growth before the winter-rest sets in; 
2 nd . because the growth in the sea is a more rapid one than in 
fresh water; whence it is possible- to distinguish rather easily on the 
scale of a fish returning from the sea: which is the part formed 
during the stay in freshwater and which is the part of the scale 
formed in the sea; and 
3 rd . because the growth, which took place in the sea in winter, 
can also be traced on the scale; in the sea the growth does not quite 
cease during that period, as is the case in freshwater; but it is 
slower there than in the other months and the rings then formed 
on the scale are in consequence narrower and separated from one 
another by nearly parallel ridges, forming together a group which 
can easily be distinguished. 
These rules to some extent might already have been deduced from 
the results of the investigations of my predecessors: I based on them 
my own researches, which I think proved useful especially for the 
determination of the age of the salmon going 1o the sea and also of 
those returning from it for the first time (the youngest of which 
are the so-called “grilse”). I limited my investigations to the salmon 
of the Rhine 1 ). The results arrived at may be dislributed over the 
following headings: a and b young salmon, one or more years old 
which have not yet left the fresh water; c young salmon (smolts) 
caught in the estuary, about to begin their life in the sea; and d 
salmon, which after having spent a certain number of months in 
the sea, begin to ascend the river. 
a. Young salmon in the first months of their life, which 
they spend in freshwater. 
The young salmon of the upper waters of the Rhine close the 
larval part of their life in the course of April — partly, however, 
as early as the beginning of that month (sometimes even at the 
end of March) and partly in the beginning of May only. They are 
no more larvae now but small fish; their yolksack is empty, and 
b My results as a whole confirm the conclusions arrived at by Johnston (l. c.) 
with regard to the growth of the scale of the salmon. However, as there seems 
to exist a remarkable, hitherto unexplained difference in the habits of the Scotch 
salmon and that of the Rhine (a difference which lately I pointed out in an 
article in the “Mededeelingen over Visscherij”, 1909, p. 128) with full acknow¬ 
ledgment of the value of the work of my predecessor, I think better for the 
moment not to enter into a comparison of Mr. Johnston’s results and mine. 
