COLOR AND COLORATION 209 
one of the earlier sections of this paper I showed that the pig- 
ment develops from before backward and, approximately, by 
segments, excepting that it may appear upon the head and 
most posterior segments simultaneously. 
“In ontogeny color appears first, as a rule, over the muscles 
which become active first, or upon certain sclerites of the body. 
These are usually the head muscles, although exceptions are 
not infrequent. It should be remembered that as the color 
appears the cuticula hardens, and, considering that muscles 
must have fixed ends for their action, it seems that there is a 
definite relation between the development of color, the hard- 
ening of the cuticula, and the beginning of muscular activity; 
the last being dependent upon the second, and, incidentally, 
accompanied by the first. As muscular activity spreads over 
the animal the cuticula hardens and color appears, so that 
color is nearly, if not. wholly, segmentally developed. 
“The relation which exists between cuticular color and the 
stiffening of the cuticula is thus a physiological one, the cutic- 
ula not being able to harden without becoming yellow or 
brown. What bearing has this upon the origin of color pat- 
terns? In the lower forms of tracheates, such as the Myria- 
pods, colors appear as segmental repetitions of spots or pig- 
mented areas which mark either important sclerites or muscle 
attachments. On the abdomens of insects, where segmenta- 
tion is best observed, color appears as well-defined, segmen- 
tally arranged spots, but on the thorax segmentation is ob- 
scured and lost upon the head. Of what importance, then, is 
pigmentation? And how did it arise? If the ontogenetic 
stages offer any basis for phylogenetic generalization, we may 
conclude that cuticula color originated in connection with the 
hardening of the integument of the ancestral tracheates as 
necessary to the muscular activity of terrestrial life. The 
primitive colors were yellows, browns and blacks, correspond- 
ing well with the surroundings in which the first terrestrial 
insects are supposed to have lived. ‘The color pattern was a 
segmental one, showing repetition of the same spots upon suc- 
cessive segments, as upon the abdomen of Coleoptera. 
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