PRICHE. 
are longitudinal muscles arranged in sets. 
each set separated from its neighbors 
by an interval of about one millimetre, 
and composed of four slender bands, 
traversing the entire length of the stom- 
ach; those next the dorsal and ventral 
lines are more prominent than the others 
and on the anterior are larger than on 
the posterior half; the sets on the dorsal 
line are united into a double band at 
the anterior extremity and pass to the 
oesophagus, where they are more widely 
separated; the oesophagus is provided 
also with other longitudinal muscles, and 
to a less extent with transverse encir- 
cling bands. The small intestine is 
covered with both transverse and _ longi- 
tudinal bands of thick white and glisten- 
ing muscular tissue ; at its anterior end 
especially, where the alimentary canal 
is greatly constricted, it is covered thick- 
ly with short longitudinal muscles, whose 
hinder extremities dovetail into other 
longer sets; besides these, there arise 
from the middle of the posterior end 
of the intestine a number of parallel 
bands of muscular fibre, which embrace 
it diagonally, passing around to the 
ventral surface of its anterior extremity ; 
starting just in front of the posterior 
insertion of these, and interlacing with 
them at right angles, is another shorter 
set of parallel muscles, whose other 
extremities are attached to the body- 
wall; still further, a set of four indepen- 
dent parallel muscular bands passes he- 
neath and supports the posterior end of 
the small intestine, reaching horizontally 
from the middle of one side of the eighth 
abdominal segment to the opposite. The 
colon is furnished simply with longitu- 
265 
dinal and transverse muscular bands, 
heavier than those on the stomach-wall. 
Digestive system. The oesophagus is 
a simple, straight, equal tube 1.5 mm. 
long, terminating posteriorly in a lar- 
ger portion swollen in the middle and 
better provided with muscular bands, 
3.9 mm. long and 1.75 mm. broad —a 
sort of crop, which extends part way 
into the second thoracic segment. The 
stomach extends from the middle of the 
second thoracic to the middle of the 
seventh abdominal segment and of coursé 
varies in size according to the amount 
of food the creature has swallowed; 
usually it is about 4 mm. in diameter ; 
the proper wall of the stomach seems to 
be the merest film, traversed by mus- 
cular fibres, which, by lines not deeply 
impressed, divide the surface into narrow, 
rounded, transverse, parallel lobes, reach- 
ing from the middle of the upper and 
under surfaces to the middle of each side, 
and which alone prevent the perfectly 
free and direct posterior motion of the 
contents. The stomach itself, however, 
may be wholiy withdrawn, without rup- 
ture, from this investing muscular tissue. 
At the middle of the seventh abdominal 
segment, the alimentary canal suddenly 
tapers, and the small intestine commen- 
ces, extending half-way to the end of 
the body and consisting of a straight 
cylindrical tube 2.25 mm. in diameter, 
surrounded by thick walls of muscular 
tissue, the longitudinal bands of which 
mold the interior walls into very promi- 
nent longitudinal ridges. The colon is 
a simple straight tube of the same size as 
the intestine but capable of considerable 
expansion, and with a smooth inner 
