ZOOLOGY FOR MEDICAL STUDENTS CHAP. 



n>iip of five ol these annuli corresponds to a single 

 ,t I'olvchaete or Oligochnete. 



is hermaphrodite, the gonad being formed from the lining 



-i'-al roelomic chambers nine (sometimes ten or eleven) 



I'.. /) situated vcntrally on each side of the mesial 



ingle pair of rather smaller rounded ovaries (ov) situated 



rd. Ovaries and testes occur in successive somites,, i.e. 



of live annuli from one another. As regards ducts, each 



prolonged into a slender oviduct (Fig. 73, C, od} one or other 



; H. h passes under the ventral nerve-cord. The two ducts unite to 



an unpaired oviduct which winds from side to side in the substance 



in -looking albumen-gland (a.g) and on emerging from this 



la i'nr\vard on itself and is continued as the thick-walled muscular 



I to the median external opening. The eggs before being laid 



.inulate in the vagina and the inner portion of this organ is conse- 



Iy sometimes termed the uterus. 



K.idi test is is continued outwards into a minute vas efiferens (Fig. 73, 



i these open at right angles into a longitudinal duct the vas 



This extends forward to the level of the somite next 



in front ol tin- ovaries where its lining becomes highly glandular. This 



glandular portion of the vas deferens is coiled into a compact mass 



epididymis (</>). IJcyoml this its wall becomes thick and muscular 



jaculatorius e.d] : it then is continued towards the middle 



Imr as ;i very narrow tube and opens into the swollen inner end 



of a thick muscular tube the penis which can be pushed 



1 1 rough the male opening. This like the female opening is unpaired 

 in the mid-ventral line, the two openings being five annuli (--one 



part. 



i the leech, fertilized in the vagina or uterus, are deposited 



ocoon. measuring about 25 mm. by 15 mm. ; secreted on the surface 



Mites in the neighbourhood of the female opening, though this 



portion of the ectoderm is not so thickened as to form a conspicuous 



< litellum as is the case in the earthworm. A thick outer 



I the cocoon is said to be deposited secondarily by the 



i the lips and to be formed possibly by the pharyngeal glands. 



i' posited in damp earth near the water margin. 



nervous system of the leech is arranged on the same general 



! nmhricns. the only important difference being that the 



the two ends of the ventral nerve-cord are crowded together 



! Thus i he rircum oesophageal commissures pass ventrally 



"presenting the first five ganglia of the ventral 



