105 
muscle wall in the Family Stylochidae, the members of which are 
characterized by their unusual firmness of body. This is actually 
to a great extent caused by the strength of the subdermal muscle 
walls and the large amount of dorso-ventral muscle bundles. The 
latter kind of fibres is in the new species very delicate and fine 
and is never present in excessive numbers. 
The pharynx is only moderately folded. The pharyngeal chamber 
is not large, and the side-pockets are small and insignificant (text-fig. 
5 ). The latter feature is very unusual in Stylochids. The intestine 
shows ordinary conditions. The coeca are thick, beadlike, and do 
not anastomose. They are rather sparsely arranged, which makes 
it easy to trace their course and branching in toto preparations 
(text-fig. 7). 
The testes and ovaries have the usual location. The latter are 
very scattered and in the present specimen as yet immature. The 
testes, on the other hånd, are fully ripe and extremely abundant, 
and are arranged in a dense, often compact layer. The seminal 
canals (sc) originate on the sides of the pharynx and, slightly 
converging, continue in a sinuous course back- 
wards. In their most caudal part, their course is 
changed, becoming more straight (Fig. 8), and at 
the same time they are provided with a somewhat 
stronger muscularis. But this does not at all reach 
such a strength that one is entitled to speak of 
a clear development of false seminal vesicles; 
further, the lumen is not widened in any pro- 
nounced way. Considering these circumstances, 
one would expect to meet a true seminal vesicle; 
i. e. an unpaired, median vesicle, in the animal, 
but this is, however, not the case. After the fusion 
of the two seminal canals, the ductus ejaculatorius 
thus formed proceeds without thickening or dilation 
in a straight course backwards and opens together 
with the vesicula granulorum into the antrum. The 
antrum masculinum, of fairly average dimensions, 
is to its greater part filled with a thick promin- 
ence of a half-globular shape (Plate IV, Fig. 22). This formation 
represents the penis, but is not traversed along its entire length 
Ilyplana aberrans. 
Fosteriorend of the 
body in ventral 
aspect. 24 x. 
fvs, the homologue 
to a false seminal 
vesicle; sc, large 
seminal canal. 
