224 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. 
different fate; for the “blood,” or hemolymph, of the chrysalis enters 
them, and they become completely filled with the fluid. This hamo- 
lymph, when found in the blood sinuses of the chrysalis, is a clear amber- 
yellow fluid, but when taken from the pupa, and exposed to the air, it 
soon loses its translucency and becomes of a turbid ochre-yellow color. 
Some such change as this seems to come over the hemolymph when it 
enters the scales, for they always exhibit a dull ochre-yellow color, which 
is exactly similar to that displayed by the haemolymph a few minutes 
after it has been removed from the chrysalis. No matter what pig- 
mental color the scales are ultimately destined to display, they all go 
through this ochre-yellow stage. 
We will here digress a moment to describe the very exceptional cir- 
cumstances which occur during this period in those scales that are found 
upon the nervures and at the outer edges of the wings in Danais plexip- 
pus. These scales are about twice as large as those that are found be- 
tween the nervures. They are so large, indeed, that leucocytes may 
pass into them ; and, as a matter of fact, a single leucocyte enters each 
one of them. There are two sizes of leucocytes to be found within the 
lumen of the pupal wings. The larger ones (Plate 6, Figs. 48 and 52 
have about twice the diameter of the smaller (Figs. 47, 49, 50, and 51). 
The smaller ones are by far the commoner, and they are the only ones 
that ever enter the scales. As soon as the leucocyte enters the scale it 
begins to degenerate, and finally to break down and disintegrate. Suc- 
cessive stages in this degeneration are shown in Plate 6, Figs. 39, 40, 
41, 42, 33, and 43. 
Figure 39 (Plate 6) is a drawing of a leucocyte that has apparently 
just entered the scale. The chromatin has shrunk into a small, deeply 
staining ball, and lies near the centre of the clear vesicular nucleus. Tt 
will be seen that the condition of its nucleus is quite different from that 
of the leucocytes which float free in the lumen of the wings. My rea- 
son for assuming that the leucocyte represented in Figure 39 has only 
recently entered the scale is, that it is the only one of many hundreds 
observed by me which showed any trace of chromatin within its nuclear 
membrane. In most of the leucocytes which one sees in the scales the 
nuclear membrane has disappeared and the chromatin is scattered through 
the whole cell (Figs. 41 and 42). I therefore conclude that the period 
during which the nucleus remains in an approximately normal healthy 
condition is very short. Disintegrating leucocytes are shown in Plate 6, 
Figs. 33 and 43. It is interesting to note that the leucocytes enter 
only the large scales, those upon the nervures and upon the edges of the 
