INTEGUMENT OF NECTURUS MACULOSUS 523 
to contract. When the larvae are placed in a cold room (4° 
to 12°C.) the melanophores are always completely expanded, 
whether the animals be kept in total darkness or brightly illu- 
mined on white or indifferent background. Hence in Ambly- 
stoma, up to 12°C., temperature is more effective than either 
light or background. The effects of high temperature are not 
so noticeable as those of low, and complete contraction is never 
obtained by warming the animals. 
2. In Necturus. The effects of difference in temperature on 
the melanophores of Necturus are not very apparent. Animals 
kept in a bright light, whether on a white, indifferent, or black 
background, are always dark, irrespective of changes in temper- 
ature. In darkness at low temperatures (9° to 10°C.) maximum 
contraction of the melanophores always results. Above 10°C. 
and up to 20°C., the response does not appear to be greatly 
changed, but quite often at the upper limit of temperature the 
contraction is not complete. Temperatures above 20°C. always 
appear to inhibit the contracting effects of darkness, and at 25°C. 
the chromatophores usually remain completely expanded as in 
bright light. High temperatures (25°C. and over), therefore, 
are more effective stimuli than darkness, but, in the light, low 
temperatures do not appear to have any appreciable effect on 
coloration. 
It has been shown that Necturus differs from all Amphibia, 
except the tadpoles of Rana pipiens, in its responses to illumina- 
tion and darkness. In the majority of animals high temperatures 
bring about the same results as light, and low temperatures have 
the same effect as darkness. It is not surprising, then, to find 
in Necturus that high temperatures, similarly to light, cause an 
expansion of the melanophores, where in other animals a con- 
traction is always observed. Hooker (’14 a) does not give any 
information regarding the effects of temperature on the coloration 
of tadpoles, and no writer has described for Amphibia an expan- 
sion of chromatophores due to high temperature. However, in 
certain fishes (von Frisch, ’11 a, 11 b) a high temperature brings 
about an expansion of the melanophores. 
