SEGMENTED WORMS OR ANNELIDA. 



more capacious towards the hind end, the largest terminal 

 pair forming two great sacs on each side of the comparatively 

 narrow posterior part of the gut. As all the pockets point 



more or less backwards, it 

 is evident that a leech to 

 be emptied of the blood 

 which it has sucked must 

 be pressed from behind 

 forwards. The pockets 

 filled, the leech drops off 

 its victim, seeks to retire 

 into more private life, and 

 digests at leisure. The 

 digestion does not take 

 place in the pockets, but 

 in a small area just above 

 the beginning of the 

 terminal part or rectum. 

 This rectum, running be- 

 tween the two last pockets, 

 is separable from the true 

 stomach just mentioned 

 by a closing or sphincter 

 muscle. It ends in a 

 dorsal anus above the hind 

 sucker. 



Vascular system. — Two 

 main lateral vessels run 

 longitudinally, one on each 

 side of the body. They 

 are connected with one 

 another by looping ves- 

 sels, give off numer- 



Fig. 93. — Dissection of leech. 

 — After Bourne. 



e.g., Cerebral ganglia ; f., penis; 

 s.z'., is opposite the seminal vesicle; 

 ov.f ovary; ut., uterus; vd., vas 

 deferens ; Lb. v., lateral blood 

 vessel; _ T.4, fourth testis ; n.v., 

 nephridial vesicle; N.17, last ne- 

 phridium ; G. 19, nineteenth pair 

 of ganglia; n.c, nerve-cord. 



