( 495 ) 
fall in temperature in winter is by no means so considerable as 
in the river: there is never any question of the sea freezing and 
an absolute cessation of the growth in consequence. Yet even there 
down to the bottom and also in deeper water the vital processes 
in winter are more or less dependent on the surface, which is more 
directly under the influence of sunshine or of atmospherical pheno¬ 
mena in general. Now that lesser activity of all the vital processes 
can be traced on the surface of the scale in the shape of a sometimes 
narrower, sometimes broader group of narrow rings of growth be¬ 
tween the others developed in the sea, and which as a rule are much 
broader. The part of the scale formed in the sea is recognised at 
first sight: here the lines of growth run at a greater distance from 
one another; they are more loose and irregular when compared with 
the nearly smooth and parallel lines on the part formed in fresh¬ 
water. The marine part, moreover, is as a rule formed more quickly 
than the freshwater-part, which is quite in accordance with the more 
rapid development of the whole body. We saw that the length a 
young salmon has at the end of the first year is 16 cm. at most 
and that, in freshwater, as a rule they do not reach 20 cm. in their 
second year. If, however, such a young fish of 16 cm. at most 
descends to the sea in May of a certain year, it may come back 
next year in July or August as a grilse of a length of 55 — 57 cm. 
The figures 17 and 17a were drawn from a scale of such a grilse. 
There is no doubt in my mind, that we have to do with a young 
fish hatched in the spring of 1907, which had a good development 
during its first year and which found its way to the sea in May 
1908. Its length at that time was 16 cm. at most and its weight 
may have been 55—60 grams. In the sea it grew rapidly during a 
period of one year and‘three months and in August of the following 
year it came back from the sea as a fish of a length of 55 cm. 
and of a weight of 1.44 kilogrammes. x ) 
Only part and a relatively small part of the smolts which have 
migrated to the sea, return so soon. Part already of those returning 
as grilse stayed a second winter in salt water before beginning their 
ascent of the river. Of such an older grilse (of a length of 64 cm.) a 
~Vln the natural history of the salmon this is a point which has always given 
Tise to great controversy and on which even now no general agreement exists. 
1 may remind the reader of the famous “Stormontfield experiments” so often 
cited in the literature of the subject, which (1854-61) were taken with marked 
fishes and which should have proved that smolts of half an ounce weight, which 
went to the sea in May, returned six weeks later to the river as grilse of a weight 
of &U pounds. 1 think we may say now, that even in the sea salmon do not grow 
with such rapidity. 
