MUNSON: SPERMATOGENESIS OF PAPILIO. 
49 
active vital processes are at their lowest ebb, for I find that at this 
stage mitosis is practically arrested even in the germ cells; (3) in both, 
the outer cuticle thickens and hardens, causing in the willow falling 
of the leaves bv the formation of a corky ring around the base of the 
petiole, and causing in the larva the shedding of its head probably by 
a similar hardening of the cuticle. The changes of color in both are 
apparently due to this thickening of the cuticle, the withdrawal of 
fluids to deeper parts, the hardening and stiffening of the cells covering 
the body, and even to a certain extent affecting the internal metabolism 
of the deeper tissue cells, causing changes in the optical properties 
of the cell pigments. 
Development of Sex. 
I have not studied the embryology of Papilio rutulus . The facts 
regarding the early development of the genital organs in both sexes, 
I can onlv infer from what I have seen in the fullv formed larva, both 
male and female. It is often affirmed that sex is not inherited, and 
that its determination depends on external conditions such as tempera¬ 
ture and food. The experiments of Treat (’ 73 ) certainly suggest 
such a conclusion. 
In this form the sex is determined early, as in the larva it is an easy 
matter to distinguish between ovary and testis. It is evident that 
originally the two must be very similar, for both have the general 
characters of a gland, a right one and a left one, each consisting of a 
simple tube or duct, the oviduct or vas deferens, leading from four 
simple chambers or follicles, which constitute the ovary as well as the 
testis. In the ovary these follicles remain distinct and elongate into 
tubes, while in the testis, they become closely applied to one another, 
and are invested (like the ovary) with three coats forming one spherical 
body. Then the right and left testes finally become closely applied 
to each other, constituting thus a double organ characterized by a 
deep red coloration arising from pigment developed in the inner 
investing coat, really the original epithelium of the gland. 
Although the female is the first to emerge in the spring, the ovary 
in the larva is comparatively less developed than is the testis. I 
have found in the male larva the sex cells in the spermatid stage when 
the oldest egg was in its first stages of growth. Possibly the phenomena 
