The Cyclostomes, or Lampreys 497 



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 tlie 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. 

 When they migrate, the}? stop at the site that seems to suit their 

 fancy, many stopping near the lake, others pushing on four 

 or five miles farther up-stream. AVe have noted, however, 

 that later in the season the lower courses become more crowded, 

 showing that the late comers do not attempt to push up-stream 

 as far as those that came earlier. Also it thus follows, from 

 what was just said about late-running females, that in the latter 

 part of the season the lower spawning beds are especially crowded 

 with females. In fact, during the early part of the month of 

 June we have found, not more than half a mile above the lowest 

 spawning bed, as many as five females on a spawning nest with 

 but one male; and in that immediate vicinity many nests 

 indeed were found at that time with two or three females and 

 but one male. 



" Having arrived at a shoal which seems tn present suitable 

 conditions for a spawning nest, the inrlividual or pair commences 

 at once to move stones with its mouth from the centre to the 

 margin of an area one or two feet in diameter. When many 

 stones are thus placed, especially at the upper edge, and they 

 are cleaned quite free of sediment and alg;e, both by being 

 moved and by being fanned with the tail, and wlien the proper 

 condition of sand is '"ound in the bottom of the basin thus formed. 



