Translation Series No.1211

that are still problems for us. Thus already in the nineteenth century the
threat of overtishing different waters had been pointed out. This call has
been constantly repeated until today. It must, however, be mentiohed that
such warnings were fOrmerly based more on intuition than on exact knowledge.
Very much up to date appears the demand for tagging experiments
by A. Fritsch (1893) and apparently little has changed until today, when
one reads his remark that such expensive experiments were probably possible
only in America.
A review cif the problems posed in the literature on salmon shows
that the statement by K. A. Pyef inch that the fundamental knowledge of the
biology of the salmon has increased only little up .to the present day, can
only mean that, although the older researchers actually did describe the
life cycle of the salmon in its main outlines, it required later a great .
deal of effort to provide exact proof for these statements. Even if Gessner
considered already in 1558 the parr to be the young stage of the salmon, it
remained for J. Shaw (1836, 1838) to provide the scientific proof for this
assumption through a laboratory experiment. Furthermore, it must not be
forgotten that only a few -sta.'t4en-s of the so-called life.cycle had been
described, such as the ascent of the salmon into the rivers and the spawning.
Today the river stage is well known in its sequence and one works now on
partial problems in order to understand the governing mechanisms for certain
effects. The majority of the publications until long after the turn of the
century had a purely descriptive character. Today, however, very special
questions are being studied that are supposed to contribute to the explan-
ation of the causality of the phenomena. This is the one difference that
distinguishes present day investigations from the older'ones.
A further change consiste in that besidea the individuarbeing