The family Amphilinidae contains two genera, Amphilina from the coelome of the Sturgeon, Amphiptyches from the intestine of Chimaera. The body is flat, and like that of a Distome, with a sucker at its anterior pole. In Amphilina a number of unicellular glands open into the sucker1, and are surrounded by the retractor muscles of that structure. Its nervous system consists of two anterior swellings connected by a transverse commissure, and two lateral nerves, which unite posteriorly and give off branches. The testes are vesicular; the vas deferens opens posteriorly; the germarium is single, the vitellaria double, one on each side, and structurally resembling the same organs in a Trematode; the vagina opens near the vas deferens, the uterus anteriorly. The embryo is ciliated anteriorly, and has ten hooks. The family has been supposed to connect the Cestoda and Trematoda. Cf. Lang, Mitth. Zool. Stat. Naples, ii. 1881, p. 394; Salensky, Z. W. Z. xxiv. 1874; Grimm, Z. W. Z. xxv. 1875. Amphiptyches, Wagener, Archiv f. Anat. und Physiol. 1852; cf.

Id. A. N. 24, I, 1858.

The Class is divisible into the following groups, the value of which is uncertain, but they are generally regarded as families.

1. Taeniadae: head provided with four suckers, and sometimes with a single or double circlet of hooks. Proglottides well-defined and cast off. No uterine aperture. Taenia, Ptychophysa ?, Dipylidium ?

2. Tetraphyllidae: head with four very mobile and distinct suckers. Proglottides well-defined and cast off; inhabit Selachians. Subdivisible into (a) Phyllo-bothridae, e. g. Echineibothrium, Phyllobothrium; and (b) Phyllacanthinae, with two to four hooks to each sucker, e. g. Calliobothrium.

3. Tetrarhynchidae (= Phyllorhynchidae): head provided with four suckers and four protractile proboscides armed with hooks. Non-sexual form occurs chiefly in Teleostean fishes, the sexual in Elasmobranchii. Tetrarhynchus.

4. Diphyllidea: the neck and two suckers armed with hooks. Echinobothrium, in the Ray.

1 Traces of this sucker are found together with glands in some Tetrarhynchidae. See Lang,;ited below.

5. Pseudophyllidea: head provided with two sucking grooves. Proglottides not always well defined. A uterine aperture. Embryo, so far as known, ciliated, and egg-shell provided with an operculum. Bothriocephalus, Triaenophorus (= Tri-cuspidaria), Solenophorus, Schistocephalus, Ligula. The genus Duthiersia appears to belong here.

6.Caryophyllaeidae: no proglottides. Head end expanded and mobile. ? development. Caryophyllaeus, from the intestines of Cyprinoid fishes.

7.Amphilinidae: supra, p. 665.

The position of the genus Leuckartia of Moniez, and P. J. van Beneden's Abothrium, is uncertain.

For lit. see pp. 228, 238.

Duthiersia (from Varanus), Perrier, A. Z. Expt. ii. 1873. Leuckartia (from Salmon), Moniez, 'Les Cestodes,' Travaux Zool. Inst. Lille, iii. pt. 2. Abothrium (from Cod), Id. ibid. Polypocephalus (from Rhinobatis), Braun, Arb. Zool. Zoot. Inst. Wurzburg, iv. 1877-78. Echinoccoid from the Earthivorm, Leuckart, 'Para-siten,' i. (ed. 2) p. 464.

Origin of Cestodes, Schneider, in his Zool. Beitrage, i. 1885.

Head of Tetrarhynchus, Pintner, Arb. Zool. Inst. Wien, iii. 1881.

Nervous system of Tetrarhynchus, Lang, Mitth. Zool. Stat. Naples, ii. 1881; of Ligula, Schistocephalus, and Bothriocephalus, Niemiec, Arb. Zool. Inst. Wien, vii. (1), 1886.

Genital organs of T. litterata, Zschokke, Z. A. viii. 1885; of T. elliptica and Triaenophorus, Steudener, Abhandl. Natf. Ges. zu Halle, xiii. 1877.

Direct development of T. serrata (!), Megnin, A. N. H. (5) xi. 1883. Cysticercus racemosus (a form of C. cellulosae), Zenker, Beitrage zur Anat. etc. als Festgabe zu Jacob Henle, Bonn, 1882. Cystic forms of Taeniae, Villot, A. Sc. N. (6), xv. 1883. Scolex of Tetrarhynchus, Hoek, Niederland. Archiv f. Zoologie, v. 1879. Embryonic development of Bothriocephalidae (= Pseudophyllidea) Schauinsland, J. Z. xix. 1885. Host of Bothriocephalus latus, Braun, Zur Entwickelungsgeschichte des breiten Bandwurmes, Studer, Wurzburg, 1883; cf. Z. A. iv., v., vi. Life history of Ligula, Donnadieu, Journal de l'Anat. et Physiol, xiii. 1877.