32 
ZOOLOGY: W. H. COLE 
Proc. N. a. S. 
by a return of normal environmental conditions after removal of the effects 
of chloretone and anoxemia. Recovery from a moribund state also is 
accompanied by contraction. 
Either expansion or contraction usually requires about thirty-six hours 
for completion, although the reactions begin within twenty minutes after 
initiation of the stimulus. Oxygen deficiency brings about complete 
expansion in about one-half hour. It is probable that any stimulus which 
lowers the metabolic rate of the whole animal also causes expansion of 
the melanophores, and any stimulus causing an increase in the metabolic 
rate results in contraction of the melanophores. 
The complete account of these investigations will appear shortly in 
the Journal oj Experimental Zoology. 
