PSTCHL. 
Silk vessels. These, which have their 
outlet upon the labium, consist first of 
a delicate thread running along the sides 
of the alimentary canal in a tortuous 
manner to the middle of the second 
thoracic segment; here, at the lower 
portion of the sides of the stomach, they 
thicken rapidly and form the second 
portion, a slender tube of uniform size, 
running in a straight course beside and 
close to the stomach as far as the middle 
of the third abdominal segment.; here it 
doubles upon itself and returns to the 
middle of the preceding segment, again 
repeating the curve in a reverse direction 
for half the distance, and then passes 
upward to the upper surface of the stom- 
ach and continues in a tortuous course, 
still hugging the alimentary canal, as 
far as the sixth abdominal segment, 
where it terminates in a very slender 
straight thread, by which it is connected 
with the sides of the intestine. The 
length of the basal thread is 12 mm., 
covering a distance of 4 mm.; the 
length of the thickened portion during 
its course on the under surface of the 
stomach is 18 mm.; during its tortuous 
course above, 35 mm. ; its normal thick- 
ness, 0.8 mm., is attained within a dis- 
tance of 2 mm. from the point. of. thick- 
ening. 
Male generative organs. The testes 
are situated in the middle of the dorsum 
of the fifth abdominal segment directly 
above and upon the stomach; they are 
269 
soft, plump, kidney-shaped, compound 
organs, 2.5 mm. long, of a bluish-purple 
color, covered by an exceedingly thin 
' whitish investment, concealing the color 
of the interior as by a pale bloom. In 
a longitudinal row along the middle of 
the inner side of each half, there are four 
minute roundish spots of a deeper color, 
each communicating with a separate 
chamber within, separated from the 
others by a thin partition wall; the 
middle pair of chambers is smaller than 
the outer one, and they are all filled with 
a grayish granular matter. From the 
anterior extremity of each testis runs a 
short white thread, not half so long as 
the testis, and thickened in the middle 
and at the end. Just behind the hind- 
most spot of each side, a delicate pellu- 
cid thread arises, which passes poste- 
riorly and a little downward until oppo- 
site the spiracle of the sixth abdominal 
segment; here it plunges downward 
toward it, and passing through the mass 
of tracheae to those of the seventh seg- 
ment, sweeps around toward the medio- 
ventral line of the body, and, passing 
through an independent muscular bundle 
scarcely larger than itself, which stretches 
transversely across the body at. this 
point, enters a whitish sac about 0.75 
mm. long, situated just beneath the ter- 
mination of the intestine; the threads 
are about 13.5 mm. long and 0.03 mm. 
in diameter. 
2.. THE PUPA OF DANAIS PLEXIPPUS, OF NORTH AMERICA. 
All the dissections were made of 
specimens either seven or nine days in 
chrysalis. 
Digestive system. The oesophagus is 
a mere thread-like vessel 0.10—0.15 
mm. in diameter, and runs straight to 
the stomach. The ‘‘jabot,” or reservoir 
above the anterior end of the stomach 
