( 494 ) 
The figure 16 represents the scale of a smolt of 21.3 cm., the 
only fish of that length caught with the smaller ones in the mouth 
of the Hollandsch Diep. At first I took that fish for a salmon over 
three years old, later on, however, I changed my opinion: I now 
think that it is a fish also about 26 months old, but one that is 
somewhat better developed. We now know, that there are young 
salmon which remain in the brooks more than two years; though it is 
probable, that these as fully three year old fish would descend to the 
sea along with those of one and two years, yet this has never been 
observed with certainty. In the upper regions of the river young 
salmon have been observed up to a length of 24 cm., such long 
ones, however, have not been seen there after August or September. 
Should this rule hold good, it would prove that an autumn-migration 
takes place consisting perhaps of larger and not very numerous 
specimens which, from being more isolated swimmers, are not so 
easily discovered as those descending in denser shoals in spring 1 ). 
d. Salmon returning from the sea. 
The smallest of the returning salmon (the grilse or Jacob-salmon 
as they are called in Holland) make their appearance in the river 
slightly earlier in one year than in another. As a rule the first are 
caught at the end of June, they are most numerous, however, in 
July and August among the salmon then ascending the river. Their 
length varies from 55— 67 cm., those of 55—60 cm. are often called 
“small” grilse and those of 64—67 cm. large ones. 
The investigation of the scales of two small grilse of 55.6 and 
57 cm. brought to. light, that these fish, which were caught in the 
lower part of the Khine on August 9 th and 14 th respect., only passed 
one winter in saltwater. A winter passed in the sea is shown on the 
scale in a somewhat other manner than is the case in freshwater. 
As has been pointed out already, the growth of the body and, in 
correspondence herewith, that of the scale ceases absolutely in t e 
frozen brooks; when the growth begins again in early spring, it mar s 
itself out on the border of the scale as a somewhat broader ring, 
(usually an extremely narrow ring first and then that broader one . 
so each winter passed in freshwater is easily .recognised. In the sea 
the salmon go to places where the water is deeper and here e 
2 ) Years ago, two young salmon of 12.5 and 14 cm. w( 
on the Merwede, which were caught in a lamprey-pot, 
instances of young salmon caught in autumn at or nea 
in Holland have not come to my knowledge. 
■ere sent to me from Gorkum 
in November 1886. Otb« 
ar the mouth of the 
