DAILY MIGRATIONS OF COPEPODS. 
123 
13. Males are positive toward females and probably chemotropically positive. 
14. Ldbidocera cestiva frequents the surface of the sea from sunset to sunrise. 
From sunrise to sunset it is presumably in deeper waters. Its migrations are 
explained as follows: Females rise to the surface with the setting of the sun, because 
they are positively phototropic to faint light and negatively geotropic; they descend 
into deep water with the rising of the sun, because they are negatively phototropic 
to strong light (their negative geotropism being overcome by their negative photo- 
tropism); the males follow the females in migration, because they are probably 
positively chemotropic toward the females. 
Cambridge, Mass., December 31, 1901. 
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