286 



THE AMERICAN NATURALIST [Vol. LV 



A NOTE ON UNILATERAL REACTIONS OF THE MELAN- 

 OPHORES OF THE HEAD IN FISHES 



Ix most discussions of the physiology of the chromatophores 

 of fishes it is apparently assumed that the reactions are strictly 

 bilateral, i.e., synchronous on the two sides. The writer, how- 

 t'ver, lias lately observed a number of cases in which the reaction 

 \v;i> rirhcr iiiiilarrral or imperfectly bila.teral. 



rpon (l< at!i. thr iii. lanophores of one side of the head in some 

 rusts Ix'coiuf all "contracted" to the extreme, while those of the 

 other side become widely "expanded." As a result, one side of 

 the head becomes very pale, the other side blackish, the two areas 

 being abruptly opposed along the mediodorsal line. This notable 



