EXPLICATION OF PLATE IX. 



All figurea without a special nomination of the species are relative to 

 Hirudo medicinalis. 

 Fig. 1 (17 X) Section of the head. 



hl. upperlip; fl. underlip; k. jaw ; ui. excretory ducts of the pro- 

 stomialglands; (g. suboesophagealganglion; sg. supraoesophageal- 

 gangUon; hk. epiderraicglands; kb. glandducts; sk. salivaryglands ; 

 oe. oesophagus; /. bloodsinus; d.s. transverse sections of muscular 

 fibres; l.s. longitudinal muscular fibres; r.s. radiar muscular fibres. 



Fig. 2 (50 X) Section of the jaw perpeudicular to its length. 



t. tcoth; kb. glandducts; k. salivary glands; s. muscular fibres. 



Fig. 3 (560 X) Section of the superior part of the jaw with tooth. 



/. tooth; c. cuticula; kb. glandducts; k. salivary glands; e. epi- 

 thelium; d.s. transverse sections of muscular fibres; t.s. transver- 

 sal muscular fibres. 



Fig. 4 (560 X) Section of the superior part of the jaw without teeth. 



Fig. 5 (300 X) Tooth of Hirudo medicinalis. 



Fig. O (300 X) Tooth of Aulastomum gulo. 



Fig. 7 (300 X) Tooth of Limnatis africana. 



Fig. 8. 9 and 10 (560 x) Parts of the epithelium of the jaw. 



c. cuticula; kb. glandducts; e. epithelium; d.s. transverse section 

 of muscular fibres; s. muscular fibres seen from aside. 



Fig. 8. 9 and 10 are successively nearer to the basis of the jaw. 



Fig. 11 (290 x) Jaw of Aulastomum gulo. 



t. tooth; c. cuticula; e. epithelium; kb. glandducts; d.s. transverse 

 section of the muscular fibres; t.s. transversal muscular fibres; h. 

 space , into which the glandducts pour out their products. 



Fig. 12 Salivary gland after solution of the granules by Na Cl 0.6%. 



Fig. 13 Salivary gland with granules. 



Fig. 14 Prostomial gland with granules. 



Fig. 15 Salivary gland, the protoplasm retracted from the wall after so- 

 lution of «the granules. 



Fig. 15 Salivary gland with strong refracting globules formed by swollen 

 granules. 



