HIRUDO MEDICINALIS LINN^US in 



the seminal vesicle with the penis is a muscular ductus ejacula- 

 torius. The penis is single and may be protruded through the 

 male genital opening which is situated in the median line on 

 the ventral surface between the fourth and fifth annuli of the 

 tenth segment. At the base of the penis is a prostata gland. 

 The female reproductive organs consist of two ovaries, two short 

 oviducts and a single muscular vagina with its female genital 

 opening between the fourth and fifth annuli of the eleventh 

 segment. 



Instructions 



1. Place a freshly killed leech on its back in a dissecting tray 

 with water and fasten it by means of two pins stuck through 

 the anterior and posterior suckers, at the same time stretching 

 it as far as possible. Find the genital openings. Make a full 

 page drawing of the ventral surface. Use the male genital 

 opening as a guide to the segmentation. Try to find the nephri- 

 diopores and the sensory papillae. 



2. Remove the pins, turn the leech over, dorsal surface up, 

 and fasten it as before. Make a sketch of the anterior five 

 segments showing the eyes. 



3. Make a superficial longitudinal median incision with a 

 very sharp scalpel in the middle segments of the body. Stick 

 two pins through the cut edges of the skin and force it apart. 

 Holding the edge of the skin with a forceps continue the incision 

 posteriorly and anteriorly gradually forcing the skin apart and 

 fastening it with pins, until the entire animal has been opened. 

 Make a full page drawing of the alimentary canal and label 

 parts. 



4. Remove with the aid of a forceps the entire alimentary 

 canal beginning with the rectum but leaving the jaws. This 

 will expose all the other organs except the dorsal sinus which 

 was destroyed by the longitudinal incision. Try to locate all 

 organs without the aid of the teacher. Make a full page drawing 

 of the male and female reproductive systems, excretory system, 



