THE HELMINTHES. 
101 
ORDER III. TREMATODES. 
The body is parenchymatous, and usually flattened. The intestinal canal, 
which is often branching, has a mouth, but nearly always is without an 
anus. 
vidual. 
The genital organs of both sexes are combined in the same indi- 
Copulatory organs are present. 
Genera : Gyrodactylus, Azine, Octobothrium, Diplozoon, Polystomum, 
Aspidocotylus,. Aspidogaster, Tristomum, Monostomum, Holostomum, 
Gasterostomum, Pentastomum.* 
ORDER IV. ACANTHOCEPHALT. 
The sack-like body is flattened, transversely striated, and swollen cylin- 
drically by the absorption of water. 
genital organs are situated in separate individuals. 
are present, 
Digestive organs are wanting. The 
Copulatory organs 
Genus: Echinorhynchus. 
ORDER V. GORDIACEL 
The body is filiform and cylindrical. 
The digestive organs are without 
an anus. The genital organs are situated upon separate individuals, 
Copulatory organs are sometimes present. 
Genera: Gordius, Mermis. 
ORDER VI. 
NEMATODES. 
The body is sack-like and cylindrical. The digestive canal has a 
mouth and an anus, and passes in a straight line through the cavity of the 
body. The genital organs are situated upon separate individuals. Copu- 
latory organs are present. 
* In this connection, and especially in reference 
to the remarks made by the author under § 99, it 
may be well to notice that Van Beneden does not 
regard the Linguatulae as true Helminthes, but 
that they belong rather to the division of articulated 
animals,—coming nearest to the Lerneae. His 
reasons are the following: 
“These animals, on their extrication from the 
‘ Besides the ring of nerves, the sub-cesophageal 
ganglion, and the cords which represent the 
ganglionic chain, the Linguatulae are provided 
with different ganglia representing the great sym- 
pathetic. I detected four perfectly distinct ganglia 
spread over the sides of the lower surface of the 
cesophagus in the new species from the Mandrill. 
In h pecies M. Blanchard detected these 
egg, are provided with two pairs of articulated feet 
terminated by hooks. 
“The nervous system differs from that of the 
Lerneae only in having two cords which form the 
ganglionic chain, separated throughout their whole 
length, whilst in the Lerneae they are separated 
for only half their length. 
“In both cases the males are comparatively 
very small, The ovisacs of the females are equally 
bulky ; but in the Lerneae which live in water 
they project externally, whilst in the Linguatulae, 
which always live in w different medium, they 
remain in the interior. 
g* 
ganglia and to-gastric nerves; but he referred 
them to the system of the nerves of relation or 
those of animal life, judging, at least, from the 
name which he has assigned to them. 
“ Another point, which, however, had not escaped 
the attention of naturalists, is that the muscles 
exhibit in their primitive fibres the transverse 
lines which are not met with in the lower ani- 
mals.” 
See Bull. de Acad. Royale de Belgique, 1848, 
XV. No. 8. See also Blanchard, Comp. Rend. 
1860, XXXI. p. 629. — Ep. 
