( 490 ) 
so they are bound to search for the necessary food in their sur¬ 
roundings. The little salmon in that stage has a length of from 
2 1 /,—3 cm. and begins to develop scales on the surface of its body. 
From a number of observations made with the aid of fish growing 
up in wild condition, and from such reared in hatcheries as well, 
we know, that the rate of growth under the same conditions in 
several specimens can be very different: at the end of September 
the parrs in the brooks which then are 6 months old may have a 
length of 6, 8 or 10 cm., those reared in a hatchery-pond at the 
same moment may vary in length from 5 to 9 cm. Their growth 
continues in autumn and seems quite to cease in winter, at least 
during a few weeks or in some years even months. When in early 
spring the animal and plant life in the brooks awakes, the young 
salmon soon begin to feed again and to continue their growth. 
Young salmon of a length of from 13 to 16 cm. observed in the 
brooks in May may be considered as fish of 13 to 14 months old, 
those of 18 to 20 cm. or a little longer are over two years old. 
Now let us control that growth with the aid of the scales. As 
questions of morphology or histology in my researches were of no 
concern, I began with investigating fish of a length of about 5 cm., 
the scales of which can easily be made out with the naked eye. 
For the study of the development of the scales in the first year it 
is an advantage, that the growth of the young salmon living in the 
brooks can be controlled, month after month, with the aid of fish 
reared in ponds; whence with regard to the growth in that period 
we have mathematical certainty, and this is in any case a good 
Starting point. 
The figures 1—10~refer to young salmon in the first year. The scale 
of the smallest fish investigated, viz. one of 4.8 cm., is figured in 
fig. 2 ; a little larger was the fish (5.5 cm.), the scale of which is 
represented in fig. 1 and la. Its shape is oval; the surface shows 
half a dozen concentric lines, which in the anterior part of the scale 
(in the figure the underpart) run close to one another and are more 
widely separated towards the other (exposed) extremity of the scale; 
five of these rings are closed, but the sixth is not: it is a regular 
occurrence in the scales of salmon, that the 5 or 6 innermost only, 
or only 5 or 6 of a certain number of innermost lines, are closed 
rings and that all the lines outside these remain open. x ) 
The scale grows with the growth of the fish and the number 0 
rings on the scale increases at the same rate. The surface seems no 
T ) This is different in the scales of brook-trout and sea-trout. A few remarks 
on the scales of these fishes will be found at the end of this paper. 
