24 Nils Hj. Odhner. 
longitudinal one of about equal thickness. Both these layers 
together equal the external one in thickness. The outer and the 
median muscle layers are continuous all round, even on the ven- 
tral side, where they form the bottom of the ventral sinus. At 
the sides of this strong diagonal cords issue, which extend towards 
the upper and lateral sides of the body. The circular muscle 
layer gives rise to a plexus of fascicles on each side of the ven- 
tral furrow, and among these are intermingled strong longitudi- 
nal muscles separate from the internal longitudinal layer. 
Between body wall and intestine a narrow space is occupied 
by the lymphatic lacunae, which carry masses of blood corpus- 
cles. They seem to be comparatively well separated from the 
ventral vessel by means of the root of the septal muscles, but 
the separation is incomplete and communication is free between 
the fibres. Among the septal muscles the pedal gland spreads 
its elements (fig. 31). The cells show in their interior numerous 
vacuoles of different sizes, and these also are distinctly observed 
in their efferent capillaries, which penetrate the epithelium inter- 
cellularly. The pedal glands are surrounded by masses of blood 
corpuscles, which also are seen in contact with the glandular 
cells; in some cases it appeared as though these were in a state 
of absorption. Outside the glandular cells and inside the ven- 
tral musculature run the pedal nerve cords. In the middle of the 
body side appear the weaker lateral nerves. 
The thin sheath forming the roof of the ventral vessel is 
closely attached to the intestinal wall. The latter forms above 
it a stripe of elevated cells bounded on each side by a furrow. 
A similar, very thick, endothelium of uniform shape is present 
ali round the intestine, except in its median dorsal line, where 
a narrow furrow runs, lined with a low ciliated epithelium 
without glands or secretory function. The diverticula of the 
intestine are spacious and not branching. 
In the specimen examined the gonads occupied a compara- 
tively narrow stripe on the dorsal side of the intestine. Their 
common transversal septum was thin and somewhat flexuous, 
bearing on its sides a single layer of (immature) eggs each cove- 
red with a thin membrane. The lateral parts of the gonads 
were filled with mature spermatids, originating from the crowded 
masses of male folliculi. The spermatids are emptied directly by 
breaking up the folliculi into the lumen of the gonad, which 
opens between the male and female portions. 
