<§> 99. 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. The genital organs of both sexes are combined in the same indi- 

 vidual. Copulatorj' organs are present. 



Genera: Gyrodactylus, Axine, Octobothrium, Diplozoon, Polystojnum, 

 Aspidocotylus, Aspidogaster, Tristomum, Monostomiem, Holostomum, 

 Gasterosto77ium, Pentastomuvi.* 



ORDER IV. ACANTHOCEPHALI. 



The sack-like body is flattened, transversely striated, and swollen cylin- 

 drically by the absorption of water. Digestive organs are wanting. The 

 genital organs are situated in separate individuals. Copulatory organs 

 are present. 



Genus : Eckinorhynckus. 



. 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 " Besides the ring of nerves, the sub-oesophageal 



to the remarks made by the author under § 99, it ganglion, and the cords which represent the 



may be well to notice that Fan Beneden does not ganglionic chain, the Linguatulae are provided 



regard the Linguatulae as true Helminthes, but with different ganglia representing the great sym- 



that they belong rather to the division of articulated pathetic. I detected four perfectly distinct gangUa 



animals, — coming nearest to the Lerneae. His spread over the sides of the lower surface of the 



reasons are the foUowmg : oesophagus m the new species from the MandrUl. 



" These animals, on then- extrication from the in another species M. Blanchard detected these 



egg, are provided with two pairs of articulated feet ganglia and stomato-gastric nerves; but he referred 



terminated by hooks. them to the system of the nerves of relation or 



" The nervous sy^m differs from that of the those of animal life, judging, at least, from the 



Lerneae only in having two cords which form the name which he has assigned to them. 



gangUonic chain, separated throughout their whole " Another pouit, which, however, had not escaped 



length, whilst in the Lerneae they are separated the attention of naturaUsts, is that the muscles 



for only half their length. exhibit in their primitive fibres the transverse 



" In both cases the males are comparatively lines which are not met with in the lower ani- 



very small. The ovisacs of the females are equally mals." 



bulky ; but in the Lerneae which live in water See Bull, de I'Acad. Royale de Belgique, 1848, 



they project externally, whilst in the iing-uaZu^ae, XV. No. 3. See also Blanchard, Comp. Bend. 



which always live in a different medium, they 1S50, XXXI. p. 629. — Ed. 

 remain in the interior. 



9# 



