MAYER: DEVELOPMENT OF WING SCALES. 229 
go, I find this to be the case. For example, if one treat the hemolymph 
of Samia cecropia with warm concentrated HNO3, it congeals into a 
deep chrome-yellow mass. If now ammonia be added in excess, it 
changes to a reddish-orange, which is very similar in color to the reddish- 
orange band that crosses the upper surface of the hind wings of the 
moth. Now this reddish-orange band of the moth is changed to chrome- 
yellow by HCI or HNO, and then, if ammonia be added, the original 
red color reappears ; this alternation of red and yellow may be produced 
indefinitely by the successive additions of ammonia and acid. Exactly 
the same sequence of reactions is produced with the red pigment derived 
from the hemolymph ; HCI or HNO, causes it to become chrome-yellow, 
and then ammonia restores the original red color. 
Another confirmatory test of a similar nature may be performed as 
follows. A portion of the drab-colored outer edge of the wing of Samia 
cecropia is treated with warm HNO; and the acid evaporated off at a 
gentle heat. By this means the pigment of the scales is changed to a 
deep chrome-yellow ; if ammonia be then added, it becomes reddish. 
Very similar reactions are obtained from the hemolymph after it has 
congealed, in the air, into a greenish-drab mass. 
Another experiment which I have tried is the following. The freshly 
drawn hemolymph from a pupa of Callosamia promethea is congealed 
by heat into a chrome-yellow colored mass; then HCl; and a small 
crystal of KClO; are added, and the acid is evaporated off at a gentle 
heat. By this means a purple mass is produced, which is changed to 
drab by HNO;. The purple spots near the outer edges of the hind 
wing of the female moth are also changed to drab by HNO;. 
Still another confirmatory experimeng may be given. The drab 
hemolymph of Callosamia promethea is dissolved and changed to a 
sepia-brown color by warm HCl, to which a crystal of KClO; is 
added. An exactly similar change occurs when the drab-colored outer 
edges of the moth’s wings are treated in a similar manner. 
It is well known that the most universal colors of the more lowly 
organized moths are the drab-gray and yellow-drab tints; and this is 
what one would expect according to my hypothesis, for these are the 
colors that are derived from the hemolymphs by mere exposure to the 
air. The brilliant yellows, reds, etc., are the result of more or less 
complex chemical processes, which have been slowly effected, probably 
through the agency of natural selection. 
In connection with the phenomena of pigmentation it is interesting to 
note that while uric acid may easily be demonstrated by the murexide 
