CONTRIBUTIONS TO THE ANATOMY OF THE HIRUDINEA. 501 



EXPLANATION OF PLATES XXIV— XXXIV, 



Illustrating Mr. A. G. Bourne's memoir " On the Hirudinea/* 



General References. 



cl. Clitellum. n. c. Nerve-cord. g}i. Ganglion, g. p. Genital pore. 

 neph. ap. Nephridial external aperture. cu. Cuticle, ep. Epidermis. der. 

 Dermis. «/. e/?. Alimentary epithelium. ^/.Gland-cell. ^/. ««. Mucous gland. 

 gl. s. Salivary gland, gl. s. d. Uucts of salivary glands, gl. cl. Clitoilar gland. 

 gl.cl.d. Ducts of clitellar glands, gl.pr. Prostomial gland, c. I. Connective 

 tissue, ma. Matrix of connective jelly, a. Indifferent connective-tissue cor- 

 puscles, b. Vacuolated cells, fat cells, c. Cells forming fibres. d,e,f. 

 Non-vascular pigmented cells, g. Cells forming botryoidal or vaso-fibrous 

 tissue. V. Vessel, s. Sinus, d. v. Dorsal vessel, d. s. Dorsal sinus. «. v. 

 Ventral vessel, v. s. Ventral sinus. I. v. Lateral vessel. /. s. Lateral sinus. 

 Ccel. Coelomic space. Ccel. ep. Coelomic epithelium, cap. Capillary vessel. 

 m. rad. Dorso-ventral or radiul muscles. m. circ. Circular body muscles. 

 m.obl. Oblique body muscles, m.long. Longitudinal body muscles. m.cut. 

 Cutaneous muscles. m, al. c. Circular muscles of the alimentary canal. 

 m. al. I. Longitudinal muscles of the alimentary canal. 



Tig. 1. — Pontobdella muricata, dorsal view. 



Fig. 2. — Similar view in outline. Somites numbered 1 — 23. — Annul! of a 

 single somite, i — iv. a. Anterior sucker, h. Posterior sucker, an. Anus. 

 c. Clitellum. 



Fig. 3. — Pontobdella muricata, opened along the median dorsal line, 

 slightly diagrammatic. c. g. Supra-oesophageal ganglion, g. 1 — 23, the 

 post-oral ganglia, ce. Passage for the oesophagus piercing the ganglionic 

 mass. n.f. Nephridial funnels. n.a. Nephridial apertures to exterior. 

 n. The nephridial network, te. 1— G, the testes, pr. The so-called pro- 

 static gland, ov. The ovaries, g. p. $ and g.p.'^ . Male and female genera- 

 tive pores. 



Fig. 4. — Hirudo medicinalis, ventral view. Somites numbered 1 — 23. 

 — Annuli of a single somite, i — v. a. Mouth, anterior sucker, b. Posterior 

 sucker, c. Clitellum. y./;. ^ . Male genital pore. _§'. ;3. ?. Female genital 

 pore. n. a. Nephridial apertures to the exterior. 



Fig. 5. — Hirudo medicinalis, opened along the median dorsal line, 

 slightly diagrammatic, cer.g. Supra-cesophageal ganglion, g. 1 — 23, the 

 post-oral ganglia, oe. Passage for the oesophagus piercing the ganglionic mass. 

 I. V. Lateral vessel. /. /. Latero-lateral branch. I. ab. Latero-abdominal 

 branch, l.d. Latero-dorsal branch, neph. 1 — 17, the seventeen pairs of 



