Part 30

PLATE 48.

Figs. 6 and 7 are from one drawing.

Fig. 6. Peripatus capensis dissected so as to shew the alimentary canal, slime glands, and salivary glands; x 3. (From a drawing by Miss Balfour.)

Fig. 7. The anterior end of Fig. 6 enlarged; x 6. (From a drawing by Miss Balfour.) The dissection is viewed from the ventral side, and the lips, L., have been cut through in the middle line behind and pulled outwards, so as to expose the jaws, j., which have been turned outwards, and the tongue, T., bearing a median row of chitinous teeth, which branches behind into two. The junction of the salivary ducts, s.d., and the opening of the median duct so formed into the buccal cavity is also shewn. The muscular pharynx, extending back into the space between the 1st and 2nd pairs of legs, is followed by a short tubular oesophagus. The latter opens into the large stomach with plicated walls, extending almost to the hind end of the animal. The stomach at its point of junction with the rectum presents an S-shaped ventro-dorsal curve.

A. Anus. at. Antenna. F.1, F.2. First and second feet. j. Jaws. L. Lips. oe. OEsophagus. or.p. Oral papilla. ph. Pharynx. R. Rectum. s.d. Salivary duct. s.g. Salivary gland. sl.d. Slime reservoir. sl.g. Portion of tubules of slime gland. st. Stomach. T. Tongue in roof of mouth.

Fig. 8. Peripatus capensis, x 4; male. (From a drawing by Miss Balfour.) Dissected so as to shew the nervous system, slime glands, ducts of the latter passing into the oral papilla, accessory glands opening on the last pair of legs (enlarged crural glands), and segmental organs, viewed from dorsal surface. The first three pairs of segmental organs consist only of the vesicle and duct leading to the exterior. The fourth and fifth pairs are larger than the succeeding, and open externally to the crural glands. The ventral nerve-cords unite behind dorsal to the rectum.

A. Anus. a.g. Accessory generative gland, or enlarged crural gland of the 17th leg. at. Antenna. c.g. Supra-oesophageal ganglia with eyes. co. Commissures between the ventral nerve-cords. d.n. Large median nerve to dorsal integument from hinder part of brain. F.1, 2, &c. Feet. g.o. Generative orifice. oe. OEsophagus. oes.co. OEsophageal commissures. or.p. Oral papilla. p.d.c. Posterior dorsal commissure between the ventral nerve-cords. ph. Pharynx. p.n. Nerves to feet, one pair from each ganglionic enlargement. sl.d. Reservoir of slime gland. sl.g. Tubules of slime gland. s.o.1, 2, 3, &c. Segmental organs. v.c. Ventral nerve-cords. v.g. Imperfect ganglia of ventral cords.

Figs. 9 and 10. Left jaw of Peripatus capensis (male), shewing reserve jaws. (From a drawing by Miss Balfour.)

Fig. 9. Inner jaw.

Fig. 10. Outer jaw.

PLATE 49.

Figs. 11-16. A series of six transverse sections through the head of Peripatus capensis.

Fig. 11. The section is taken immediately behind the junction of the supra-oesophageal ganglia, c.g., and passes through the buccal cavity, M., and jaws, o.j. and i.j.

Fig. 12. The section is taken through the hinder part of the buccal cavity at the level of the opening of the mouth into the pharynx and behind the jaws. The cuticular rod-like continuation (le.) of the inner jaw lying in a backwardly directed pit of the buccal cavity is shewn; on the right hand side the section passes through the opening of this pit.

Fig. 13. The section passes through the front part of the pharynx, and shews the opening into the latter of the median backward diverticulum of the mouth (M{1}), which receives the salivary ducts. It also shews the commencement of the ventral nerve-cords, and the backwardly projecting lobes of the brain.

Fig. 14. The section passes through the anterior part of the pharynx at the level of the second commissure (co. 2), between the ventral nerve-trunks, and shews the mass of cells developed on this commissure, which is in contact with the epithelium of the backward continuation of the buccal cavity (M{1}).

Fig. 15. Section through the point of junction of the salivary ducts with the median oral diverticulum.

Fig. 16. Section behind the pharynx through the oesophagus.

b.c. Body-cavity. C. Cutis. c.b.c. Central compartment of body-cavity. c.g. Supra-oesophageal ganglia. c.m. Layer of circular muscles. co. Commissure between ventral nerve-cords. co. 2. Second commissure between the ventral nerve-cords. co{1}. 2. Mass of cells developed on second commissure (probably sensory). c.s.d. Common duct for the two salivary glands. d.l.m. Dorsal longitudinal muscles of pharynx. d.o. Muscles serving to dilate the opening of the pharynx. Ep. Epidermis. e.n. Nerve passing outwards from ventral nerve-cord. H. Heart. i.j. Inner jaw. j.p. Jaw papillæ. L. Lips of buccal cavity. l.b.c. Lateral compartment of body-cavity. le. Rod-like cuticular continuation of inner jaw, lying in a pit of the buccal cavity. l.m. Bands of longitudinal muscles. M. Buccal cavity. M{1}. Median backward continuation of buccal cavity. m.l. Muscles of jaw lever. m.s. Muscular sheets passing from side walls of pharynx to dorsal body-wall. oe. OEsophagus. oes.co. OEsophageal commissures. o.j. Outer jaw. ph. Pharynx. s.d. Salivary duct. s.g. Salivary gland. sl.d. Reservoir of slime gland. sy. Sympathetic nerves running in muscles of tongue or pharynx. sy{1}. Origin of sympathetic nerves to pharynx. T. Tongue. v.c. Ventral nerve-cords.

Figs. 17, 18. Two longitudinal horizontal sections through the head of Peripatus capensis. Fig. 17 is the most ventral. They are both taken ventral to the cerebral ganglia. In Fig. 17 dorsal tracheal pits are shewn with tracheæ passing off from them. (Zeiss a a, Hartnack's camera.) C. Cutis. c.s.d. Common salivary duct. ep. Epidermis. i.j. Inner jaw. M. Buccal cavity. M{1}. Median backward diverticulum of mouth. o.j. Outer jaw. s.d. Salivary ducts. T. Tongue. t. Teeth on tongue. tr. Tracheæ. tr.p. Tracheal pits.

PLATE 50.

Fig. 19. "A, B, C, D, E, F, G." Seven transverse sections illustrating the structure of the supra-oesophageal ganglia. (Zeiss A, Hartnack's camera.) a. Dorso-lateral horn of white matter. b. Ventro-lateral horn of white matter. c. Postero-dorsal lobe of white matter. d. Ventral protuberance of brain. e. Central lobe of white matter. o.p. Optic ganglion.

"A. Section through anterior portions of ganglia close to the origin of the antennary nerve. B. Section a little in front of the point where the two ganglia unite. C. Section close to anterior junction of two ganglia. D. Section through origin of optic nerve on the right side. E. Section shewing origin of the optic nerve on the left side. F. Section through the dorso-median lobe of white matter. G. Section near the termination of the dorsal tongue of ganglion cells."

PLATE 51.

Fig. 20. Portion of a transverse section through the hinder part of Peripatus capensis (male). The section passes through a leg, and shews the opening of the segmental organ (o.s.), and of a crural gland, o.f.g., and the forward continuation of the enlarged crural gland of the 17th leg (f.gl.). (Zeiss a a, Hartnack's camera.) a.g. accessory gland of male (modified crural gland of last leg). C. Cutis. cl. Claw. cu. Cuticle. ep. Epidermis. f.gl. Crural gland. h. Cells in lateral compartment of body-cavity. o.f.g. Orifice of accessory foot gland. o.s. Opening of segmental organ. P. Three spinous pads on ventral surface of foot. pr. Prostate. R.M. Retractor muscle of claw. s. Vesicle of nephridium. s.c.i. Region No. 1 of coiled part of nephridium. sl.g. Tubule of slime gland. s.o.t. Terminal portion of nephridium. st. Stomach. st.e. Epithelium of stomach. v.c. Ventral nerve-cord. v.d. Vas deferens.

Fig. 21. "Longitudinal vertical section through the supra-oesophageal ganglion and oesophageal commissures of Peripatus capensis. (Zeiss a a, Hartnack.)" at. Antenna. e. Central lobe of white matter. j. Part of jaw. s.g. Salivary gland.

Fig. 22: drawn by Miss Balfour. Brain and anterior part of the ventral nerve-cords of Peripatus capensis enlarged and viewed from the ventral surface. The paired appendages (d) of the ventral surface of the brain are seen, and the pair of sympathetic nerves (sy{1}) arising from the ventral surface of the hinder part.

From the commencement of the oesophageal commissures (oes.co.) pass off on each side a pair of nerves to the jaws (j.n.).