ON PENNELLA BALZANOPTER. 42] 
though at others in patches, similar in character to those previously described in 
the spaces of the thoracic segment, whilst the contents consisted of an indefinite 
granulated, possibly a coagulated, material. The existence of these spaces in front 
of and behind the alimentary canal permits an expansion of the walls and an 
increase in the size of the lumen when the animal is feeding, and their greater 
size in the lower end of the intestine leads one to infer that the ejecta accumulate 
in it prior to expulsion. 
Two coats were readily recognised in the alimentary canal in its entire length 
—a muscular and a mucous. In favourable sections an intermediate sub-mucous 
coat was seen. The muscular coat consisted of the usual non-striped form of fibre 
an external longitudinal and an internal circular or trans- 
aitanged in two layers 
verse. In the abdominal and caudate divisions this coat was thickened, and had 
a crenulated appearance in the sections. When sections were made either longitudi- 
nally or obliquely through the canal, to enable one to obtain a view of the free 
surface of the mucous membrane, numerous slender, closely-set rugee, lying parallel 
to each other, were seen to extend longitudinally along its surface (fig. 6). In trans- 
verse sections they were cut across, and they then had the appearance of villous 
processes projecting into the lumen. It was observed in these sections that the 
sub-mucous coat formed the core of the projections, whilst the free surface was 
formed of the mucosa; obviously, therefore, they were not true villi, but were 
permanent rugze, like the circular valvule conniventes in the small intestine of the 
mammalia. At the lower end of the canal the rugze were more elongated and 
thicker than in the thoracic segment of the body. The mucous membrane was 
covered by a layer of epithelium, the cells of which in favourable specimens were 
seen to be short columns. In longitudinal or oblique sections through the canal 
in which the inner surface of the mucous membrane could be seen, the broader 
ends of the cells were recognised as forming the free surface of the mucosa. The 
lumen of the intestine contained epithelial and other débris. 
In proximity to the anus the intestine and the structures around it were specially 
modified. A short distance above the anus the intestine in transverse section was flask- 
shaped, the stalk of which was attached to the dorsal wall of chitin by a narrow mesial 
dorsal mesentery, composed of non-striped muscle, which divided the dorsal space into 
_ two lateral halves. The ventral space had not at first a corresponding division. In 
addition, muscular fibres on each side passed from the chitinous wall to the sides of the 
intestine : these fibres had the form of striped muscle, but were not definitely striated. 
The wall of chitin was lined by a strongly pigmented membrane, in which numerous 
leucocyte cells were seen, either scattered or in groups. The proper muscular wall of 
the intestine was thicker than in the upper part of the caudate segment, and the 
parallel ridges of the mucous membrane were closely set together. 
A little nearer the anus the section through the intestine was ellipsoidal, with the 
long axis directed dorsi-ventrally. The ventral space was now divided into two lateral 
