2i6 DESCRIPTIONS OF PREPARATIONS. 



stoma and Haemopis, where it is plentiful, the animal is always limp. Hirudo 

 occupies a middle position between these two extremes. 



Anatomy of the Hirudinea. A. Gibbs Bourne, Q. J. M. xxiv. 1884. Remy 

 Saint-Loup, A. Sc. N. (6) xviii. 1884. Leuckart, Die Parasiten, i. 1863, Leipzig. 

 Moquin-Tandon, Monographic de la famille des Hirudine'es, with Atlas (ed. 2), 

 1846, Paris. Leeches of Japan, Whitman, Q. J. M. xxvi. 1886. Leech, Mclntosh, 

 Encyclopaedia Brit. (ed. ix,), xiv. Genera, &c. Diesing, SB. Akad. Wien, xxxiii. 

 1858; Id. Systema Helminthum, 1850, i. p. 433, and Leuckart, op. cit. 



Somites, Whitman, op. cit. supra ; Proc. Amer. Academy, xx. (n.s. xii.) 1885, 

 or American Naturalist, xviii. 1884. 



Cuticle, hypodermis, vasifactive and botryoidal tissue. Ray Lankester, Q. J. M. 

 xx. 1880. Dark-green pigmented network of Hirudo. Joseph, Z. A. vi. 1883. 

 Muscle. Shore, Nature, xxvi. 1882, p. 493. Nerve endings in ditto. Hansen, 

 Archives de Biol. ii. 1881. 



Eyes and Segmental papillae. Whitman, Q. J. M. xxvi. 1886. Eyes. Car- 

 riere, Sehorgane der Thiere, Munchen und Leipzig, 1885 ; Ranke, Z. W. Z. xxv. 

 1875. Ditto and goblet-bodies. Ley dig, Arch. f. Anat. und Physiol. 1861 ; Id. 

 Tafeln zur Vergleich. Anatomie, Tubingen, 1864, Taf. ii. figs. 5, 7; Taf. iii. 

 figs, i, 2, 3. 



Sense-cells of hypodermis. See Gibbs Bourne, op. cit. p. 434, PI. 27, fig. 15. 



Pigment of skin. MacMunn, Proc. Birmingham Phil. Soc. iii. 1881-3, p. 389. 



43. MEDICINAL LEECH (Hirudo medidnalis), 



Prepared to show its laterally sacculated stomach and the intestine. A stiffening injection of 

 gelatine was thrown into the digestive tube, the specimen hardened in spirit and then dissected. 



THE integument has been divided down the middle dorsal line and 

 reflected to either side : the portions of the vascular system interposed be- 

 tween the digestive tract and the body-walls cut away, and the entire cavity 

 of the 'crop '.and its diverticula exposed by the removal of their dorsal 

 wall. Anteriorly to the crop is the pharynx with a villous exterior. This 

 appearance is due to the presence of numerous unicellular salivary glands 

 and to the cut ends of radial muscular fibres. The pharynx is succeeded 

 by the crop which has thin walls. Lateral diverticula or caeca which occupy 

 five-sixths of the entire body are appended to it on either side. These 

 caeca are really segmental dilatations of a central tube. There are eleven 

 of them in all. The first is small. The second appears to be double. The 

 third has much the same appearance but not so well marked. It is due to 

 the great development of a partial septum which may be seen in the suc- 

 ceeding seven caeca projecting backwards from the anterior wall. In some 

 species of Clepsine the caeca are very distinctly bifid at their outer ends. 

 The last pair of caeca, the only pair in Aulostoma, are of very great length 

 and bending sharply almost immediately at their commencement so as to 

 become apposed to each other along the middle line, are prolonged back- 



