ANNELIDA. 79 



its fellow by transverse ventral branches. Numerous branches 

 are given off to the gut, excretory organs, and reproductive 

 organs. 



The ccelom or 'body-cavity is largely filled up with connective 

 tissue, which unites the internal organs firmly together. The 

 chief ccelomic spaces are, a dorsal sinus, running above the gut, 

 and a ventral sinus surrounding the nerve-cord and connected with 

 spaces which surround the internal ends of the nephridia. These 

 sinuses have no definite walls and are simply spaces in the con- 

 nective tissue. The vessels and sinuses communicate together 

 by means of capillary networks, the chief of which are found in 



B. 



Fig. 24. LEECH. A (slightly altered after Vogt and Yung enlarged), a 

 nephridium with adjacent organs, seen from above (1) testes lobe, fol- 

 lowed by 2, 2, principal lobe, which again passes into the apical lobe, 

 3, <?; the vesicle duct, 4, arises from junction of 1 and 2, and runs to 

 vesicle 5, which opens to exterior ; sp, one of right spermaries (testes) ; 

 xpd, right spermiduct (vas deferens) ; l.v, lateral vessel of right side; 

 g, one of ventral ganglia. B (after Whitman), longitudinal section of 

 eye, much enlarged ; ep, epidermis ; gl, glandular cells of epidermis ; 

 pg, pigmented sheath; r.c, refracting cells; s.c, sense cells; n, optic 



the skin and surrounding the crop. The latter plexus is made 

 up of irregular tubules, the walls of which are composed of large 

 brown granular cells, and which constitute what is known as the 

 botryoidal tissue. 



There are no hearts as in the earthworm. The course of the 

 circulation is not accurately known. The general movements of 

 the body largely aid in the circulation. 



