“In ‘running’ they move almost entirely at night, and if
they do not reach a suitable spawning site by daylight, they
will cling to roots or stones during the day and complete their
journey the next night. This has been proven by the positive


178 The Cyclostomes, or Lampreys


observation of individuals. Of the specimens that run up
early in the season, about four-fifths are males. Thus the
males do not exactly precede the females, because we have
found the latter sex represented in the stream as early in the
season as the former, but in the earlier part of the season the
number of the males certainly greatly predominates. This pro-
portion of males gradually decreases, until in the middle of
the spawning season the sexes are about equally represented,
and toward the latter part of the season the females continue
to come until they in turn show the greater numbers. Thus
it appears very evident in general that the reproductive in-
stinct impels the most of the males to seek the spawning ground
before the most of the females do. However, it should be said
that neither the males nor the females show all of the entirely
sexually mature features when they first run up-stream in the
beginning of the season, but later they are perfectly mature
and ‘ripe’ in every regard when they first appear in the stream.
