Table for the Discrimination of the more usual Cestodes of Man and Domestic Animals.[[108]]
| I. Scolex in most cases with hooks; uterus with a median and lateral branches; yolk-glands simple, median; genital pore single; dorsal excretory vessel narrower than the ventral, without a circular commissural trunk; eggs without pyriform apparatus (processes of the ovarian membrane) | |
| Gen. Taenia L. (s. str.) | |
| A. Genital ducts pass on the ventral side of the nerve and of the two longitudinal excretory vessels | T. crassicollis Rud. |
| A. Genital ducts pass on the ventral side of the nerve and of the two longitudinal excretory vessels | |
| T. crassicollis Rud. | |
| B. Genital ducts pass between the dorsal and ventral longitudinal vessels. | |
| a. Nerve present on dorsal side of genital ducts. | |
| α. Head armed | T. solium Rud. |
| β. Head unarmed | T. saginata Goeze. |
| b. Nerve on ventral side of genital ducts. | |
| Dog-Taeniae[[109]] Head armed; genital pore marginal and — Single | |
| Many proglottides; strobila several centimetres long; small hooks with guard. | |
| Bifid hooks, which are — 230µ-260µ long[[110]]; genital pore very distinct | T. serrata Goeze. |
| Bifid hooks, which are — 230µ-260µ long[[110]]; genital pore very distinct | |
| T. serrata Goeze. | |
| — 136µ-157µ long; genital pore not very salient | T. serialis Ball. |
| — 136µ-157µ long; genital pore not very salient | |
| T. serialis Ball. | |
| Entire large hooks, which are — 180µ-220µ long; length of mature segments double their width | T. marginata Batsch. |
| Entire large hooks, which are — 180µ-220µ long; length of mature segments double their width | |
| T. marginata Batsch. | |
| — 150µ-170µ long; length of mature segments treble their width | T. coenurus Küch. |
| — 150µ-170µ long; length of mature segments treble their width | |
| T. coenurus Küch. | |
| 3-4 segments; a few mm. long | T. echinococcus v. Sieb. |
| 3-4 segments; a few mm. long | |
| T. echinococcus v. Sieb. | |
| — Double and bilateral | Dipylidium caninum L. |
| Head unarmed; two genital pores on ventral surface | Mesocestoides lineatus Goeze. |
| Head unarmed; two genital pores on ventral surface | |
| Mesocestoides lineatus Goeze. | |
| II. Scolex without hooks; one or two transverse uteri present; one or two genital pores and yolk-glands, the latter never median; genital ducts pass on the dorsal side of the nerve; eggs with pyriform apparatus. | |
| A. One transverse uterus present. | |
| a. Uterus with bullate egg-sacs; pyriform apparatus without horns; genital ducts between dorsal and ventral vessels | |
| Thysanosoma Dies. | |
| α. Head large (1.5 mm.); square lobed testes in median field; posterior margin of segments fimbriated; genital pore double | |
| T. fimbriata Dies. | |
| β. Head small; no fimbriae; pore rarely double | T. giardii Riv. |
| β. Head small; no fimbriae; pore rarely double | |
| T. giardii Riv. | |
| b. Uterus without saccular dilatations; segments short, thick, and slightly imbricate | Anoplocephala E. Blanch. |
| b. Uterus without saccular dilatations; segments short, thick, and slightly imbricate | |
| Anoplocephala E. Blanch. | |
| Horse-Taeniae. α. Head very large — No posterior lobes | A. plicata Zed. |
| — Four posterior lobes | A. perfoliata Goeze. |
| β. Head small, without posterior lobes | A. mamillana Mehl. |
| β. Head small, without posterior lobes | |
| A. mamillana Mehl. | |
| B. Two uteri and two genital pores present; horns of pyriform apparatus well developed; genital ducts pass on the dorsal side of the longitudinal vessels | |
| Moniezia R. Bl. | |
| a. Interproglottidal glands[[111]] arranged in linear series (planissima group) | |
| M. planissima S. and H. M. benedeni Mz. M. neumani Mz. | |
| b. Interproglottidal glands saccular (expansa group) | |
| M. expansa Rud. M. oblongiceps S. and H. M. trigonophora S. and H. | |
| c. Interproglottidal glands absent (denticulata group) | M. denticulata Rud. M. alba Perr. |
| c. Interproglottidal glands absent (denticulata group) | |
| M. denticulata Rud. M. alba Perr. | |
| C. Uterus single or double, without spore-like egg-sacs; eggs with a single shell; genital pores irregularly alternate; strobila narrow; testes absent from median part of the field | |
| Stilesia Raill. | |
| a. A transverse uterus in middle part of median field; head 2 mm. diameter | S. centripunctata Riv. |
| a. A transverse uterus in middle part of median field; head 2 mm. diameter | |
| S. centripunctata Riv. | |
| b. Two lateral uteri in each segment; head less than 1 mm. in diameter | S. globipunctata Riv. |
| b. Two lateral uteri in each segment; head less than 1 mm. in diameter | |
| S. globipunctata Riv. | |
| III. Scolex almost invariably provided with hooks; genital pores on left border of segment; eggs with three shells but no cornua. Segments broader than long; posterior angles salient. | |
| Hymenolepis Weinl. | |
| a. Scolex with a single series of 24-30 hooks, each 14-18µ long | |
| H. nana v. Sieb. H. murina Duj. | |
| b. Scolex very small, unarmed | H. diminuta Rud. |
| IV. Scolex provided with two elongated muscular pits. Body segmented; three genital apertures in middle of ventral surface | |
| Bothriocephalus Rud. | |
| Body 2-20 metres in length | |
| B. latus Brems. B. cristatus Dav. (doubtful species). B. cordatus Leuck. B. mansoni Cobb. (= B. liguloides Leuck.) | |
Classification of Cestodes.—The following classification, which, so far as the Taeniidae are concerned, follows that employed by Railliet, Blanchard, and most recent writers, includes only a few representative genera:—
| 1. Fam. | Cestodariidae Mont. (Monozoa Lang). | |
| Gen. | Caryophyllaeus, Archigetes, Gyrocotyle, Amphilina. | |
| 2. Fam. | Bothriocephalidae. | |
| Sub-Fam. 1. | Bothriocephalinae. Gen. Bothriocephalus, Schistocephalus, Triaenophorus (= Tricuspidaria). | |
| Sub-Fam. 2. | Ligulinae. Gen. Ligula. | |
| Sub-Fam. 3. | Solenophorinae. Gen. Solenophorus, Duthiersia. | |
| Sub-Fam. 4. | Diphyllinae. Gen. Echinobothrium. | |
| 3. Fam. | Tetrarhynchidae. | |
| Gen. | Tetrarhynchus. | |
| 4. Fam. | Tetraphyllidae. | |
| Sub-Fam. 1. | Phyllobothrinae. Gen. Phyllobothrium, Echeneibothrium, etc. | |
| Sub-Fam. 2. | Phyllacanthinae. Gen. Calliobothrium, Anthobothrium, etc. | |
| 5. Fam. | Taeniidae. | |
| Sub-Fam. 1. | Cystotaeninae. Gen. Taenia s. str. | |
| Sub-Fam. 2. | Anoplocephalinae. Gen. Moniezia, Thysanosoma, Stilesia, Anoplocephala. | |
| Sub-Fam. 3. | Cystoidotaeninae. Gen. Dipylidium, Hymenolepis, Drepanidotaenia, Dicranotaenia, Echinocotyle, Davainea. | |
| Sub-Fam. 4. | Mesocestoidinae. Gen. Mesocestoides, Dithyridium. | |
| Sub-Fam. 5. | Ichthyotaeninae. Gen. Ichthyotaenia, Corallobothrium. | |
CHAPTER IV
MESOZOA
DICYEMIDAE—STRUCTURE—REPRODUCTION—OCCURRENCE: ORTHONECTIDAE—OCCURRENCE—STRUCTURE: TRICHOPLAX: SALINELLA.
The Mesozoa are an obscure group, the position of which in the animal kingdom is still doubtful. The name Mesozoa was given to the group by its discoverer, E. van Beneden,[[112]] as he concluded that they were intermediate between the Protozoa and the higher Invertebrates. Recent authors, however, have called attention to the resemblance existing between them and the "sporocysts" of Trematodes, and though we still are ignorant of certain important points in their life-histories, the Mesozoa are most conveniently (and probably rightly) considered as an appendix to the Platyhelminthes.
Fig. 45.—A, B, C, Stages in the development of the vermiform larva in Dicyema typus van Ben. (After Ed. van Beneden.) cal, "Calotte"; gc, germinal cell; n, nucleus of endodermal cell.