Paper fe 297 
plunges downward to just above the 
oesophagus in advance of the crop, then 
passes rapidly upward again to the in- 
tegument, which it follows to the middle 
of the mesothorax, diminished to half its 
former size, so as to appear a mere thread, 
and then, casting free again. passes for- 
ward as in the larva, reaching the 
oesophagus again in the prothorax, where 
it appears to be attached to something, 
which was not made out; beyond this 
point it was not traced. 
Nervous system. Between the cephalic 
and thoracic ganglia the nervous cord 
is moderately broad, flattened and 
double ; the thoracic ganglion is situated 
in the front part of the mesothorax ; it 
is oval and evidently composed of two un- 
equal, anterior and posterior, elements, 
for slightly in front of the middle it is 
pierced by a vertical passage of consid- 
erable size, and the portion in front of 
it has a slight, independent tumidity ; 
the whole is a little more than 1.5 mm. 
long and less than half as broad, taper- 
ing posteriorly; from near the middle 
it emits lateral nerves, which pass toward 
the wings, and just before the hinder 
end a rather prominent nerve, which 
runs backward, parallel to the main cord 
and nearly as large as it, half way to the 
abdomen, evidently feeding the legs; 
besides these there is another similar 
pair, also running backward but divari- 
eating a little, which originates from the 
widest part of the posterior portion. 
The cord itself is rather slender, and 
runs without enlarging until it reaches 
the abdomen, when it appears gradually 
to thicken and form a pseudoganglion 
of an elongate, fusiform shape, nearly 1.5 
mm. long and terminating just before 
the first abdominal ganglion; this ap- 
pearance, however, is produced by the 
fact that throughout the abdomen the 
cord is overlaid by an investment mainly 
pellucid, but not pellucid enough to 
allow the true cord to be seen, except- 
ing from beneath; this investment does 
not cover the ganglia to an equal extent, 
but only as a film; so that the abdom- 
inal development of the nervous system 
is an exceedingly delicate cord, expand- 
ing at four different points into lenticu- 
lar, disk-like ganglia of a small size, but 
many times exceeding the cord in 
diameter, the whole enwrapped in a 
semi-pellucid investment which makes 
it appear .of nearly uniform diameter, 
excepting in front of the first true ab- 
dominal ganglion, where the investment 
becomes swollen and less pellucid, re- 
sembling a greatly elongated ganglion. 
The abdominal ganglia are 2.25 mm. 
apart ; the first, which is scarcely broader 
than the cord, and noticeable mainly by its 
whitish color, is situated near the end of 
the second segment; the second at the 
beginning of the fourth; the third at the 
beginning of the fifth, and the last in the 
middle of the sixth segment; the last is 
larger than the others and emits four 
delicate posterior nerves; each of the 
abdominal ganglia is also provided with 
lateral nerves, similar to, but more deli- 
cate than, those of the larva. 
In Newport’s observations on the 
changes in the nervous cord of Aglais 
urticae,* he shows a more considerable 
change between forty-eight and fifty- 
eight hours than perhaps between any 
others of the stages he has drawn and 
*Phil. trans., 1834, p. 412-416, pl. 15-16. 
