12 



BERTRAM G. SMITH. 



In lots 1 , 3 and 4 the sexes were determined by dissection. 

 Since in only one of these specimens the secondary sexual char- 

 acters were those of the opposite sex, the probable error in deter- 

 mining the sex by the external characters is a negligible quantity. 

 In lot 2 the sexes were determined by the external characters. 



These results are sufficient to indicate a decided preponderance 

 in the number of males on the spawning ground at the spawning 

 season, though not necessarily at other times or places. 



Spaivning Behavior. — The casual observer will find schools 

 of Chrosomus occurring in the pools and the deeper portions of 

 the swift water of the brook. On quietly approaching the stream, 

 one will often notice a splashing of the water of the shallow rapids, 

 scarcely distinguishable from the ordinary rippling of the current. 

 Further observation will reveal the fact that in places the water 

 is alive with tiny fishes, struggling and crowding one another in 

 water so shallow that the suface is violently agitated ; occasion- 

 ally a mass of wriggling fishes will flash into view at the very 

 surface, or crowd splashing upon the pebbly shore, where some 

 may be left stranded, later to struggle back into the water. 



When alarmed, the fishes almost invariably swim up stream 

 from the shallows. In the deeper water they gradually recover 

 from their fright ; those that have hidden amongst the water 

 vegetation or under the shadow of overhanging banks, rejoin 

 the school. Together, moving in unison like a flock of sheep, 

 they surge slowly down stream ; but before they reach the shal- 

 low water again, they face about with an eddying movement, and 

 swim up stream. This circuit is made repeatedly, the school 

 drifting each time a little farther down stream toward their proper 

 spawning grounds. The behavior of the fishes from the time 

 they are frightened away from the shallows, until they resume 



