BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
test in the fluids of the alimentary tract of the pupc of the Saturnidie, 
it is never present in the hemolymph of the imago ; nor can I detect 
it in the drab-colored pigment of the outer edges of the wings. The 
amount of uric acid in the fluids of the alimentary tract of the pupa 
increases as the pupa becomes older, so that the fluid which is voided 
upon emergence is always strongly impregnated witb it. In the case of 
Pieris rap there is no uric acid either in the alimentary tract or haemo- 
lymph of the larva, but it is present in the alimentary tract of tho 
pupa. It seems to me probable that the uric acid of the alimentary 
tract of the pupa may be a product of the metabolism of the hamolymph 
that is removed from the fluids of the body by the Malpighian tubules. 
4. Summary of Conclusions believed to be New to Science. 
1. It has been shown by Schäffer (89), van Bemmelen (’89), Urech 
(91), and Haase (92) that the order of development of the colors upon 
the pupal wings of the Lepidoptera is as follows. During early pupal 
life the wings are as transparent as glass, but about ten days before 
emergence they become opaque and pure white. Soon after this a dull 
yellow or drab color suffuses the wings, tingeing all parts excepting 
those that are destined to become the white spots of the mature wing ; 
these always remain pure white. About twenty-four hours after the 
appearance of the dull yellow suffusion the mature colors begin to appear 
in places near the centre of the wing. 
In addition to these facts, I have shown that the transparent condition 
of the wings corresponds to the period before the scales are formed, and 
to the time when they are still completely full of protoplasm. The 
white condition is caused by the withdrawal of the protoplasm from 
the scales, leaving them as little hollow bags filled with air. In this 
condition they diffract tho light and appear pure white. 
After the protoplasm has completely withdrawn from the scales, tho 
“blood,” or hemolymph, of the pupa enters them, and soon after this 
the wing becomes of a uniform dull yellow or light drab color. This 
color is due to the fact that soon after the hamolymph has entered the 
scales it changes to a dull ochre-yellow, and finally to a drab color. The 
same change takes place in haemolymph which has been removed from 
the pupa and exposed to the air. The mature colors are due to chemical 
changes in the hemolymph itself. They first appear in places between 
the nervures, never upon the nervures themselves. The last places to 
