( 492 ) 
b. Young salmon, which at the end of their first year do not leave 
the upper course of the river. 
From April or May, in numerous brooks of the upper course, it is 
not so difficult to catch young salmon of a length of 13 cm. and 
more. It is not possible that these were born in the same year and 
they must be over one year old in consequence. How it is, that 
part of the young salmon remain behind on the upper course, when 
the great majority set out for the main river and the sea in early 
spring, is not sufficiently explained. We only know, that sex is con¬ 
cerned in the matter: a very large percentage of the remainder, one 
year old fish, are males and the still older ones are, as far I could 
investigate, all males and all these males become mature and spawn 
before going to the sea. It is obvious, therefore, that the remaining 
behind is connected with the early development of maturity in the 
males; yet the question is a somewhat complicated one 1. because 
other males (and most probably th,e greater part) descend to the sea 
along with the females at the end of the first year; and 2. because 
some females also remain in the river at the end of the first year. 
The unequal growth, which in the salmon of the first year is so 
striking, seems to continue to exercise its influence; to control the 
age, therefore, the growth alone is of little use: the structure of the 
scales renders excellent services in the matter. In May you can catch 
small salmon in the upper course of the Rhine from 13 to 20 cm. 
long; in July as long as 24 cm.; in August of the same size, but 
also some of 13, 14 etc. cm.; in September larger ones of 20 and 
more cm. but still some of from 15 to 17 cm. and even in October 
and November the smallest salmon caught, were not longer than 14 cm. 
The figures 11—13 were drawn from scales of such salmon: 
figures 11 and 12 are both from those of salmon caught in August. 
Both show the formation of the first year and around it what has 
been formed since the beginning of the second year. Whereas t e 
one salmon (fig. 11) in the first year developed only insufficien y 
— as may be concluded from the small dimension and the sma^ 
number of lines of the first year’s scale — the scale of fig- 
of a much better grown fish. Comparing fig. 13 with the 
ones, little doubt remains as to the age of this salmon: it is a 
of a length of over 20 cm. caught in the Kinzig in May, 
spent two whole years in the upper course of the river, an w 
on being caught, was in the beginning of its third year. The * ^ 
of the parts formed in the one and the next year in these ^ 
present themselves as a somewhat more prominent line; ter 
