HIRUDIN E A 135 



which is even more pronounced in Hirudo. The tubules con- 

 sist of simple or branched cells with an intracellular lumen, 

 they unite at intervals, increase in size, and open by an inter- 

 cellular duct at 10 external pores. £ranchellion and Fiscicola 

 probably possess a similar nephridial network. 



Clepsine. and Hirudo have paired nephridia distinct from 

 one another. The funnel in Hirvdo lies in the same blood 

 sinus as the testis (Figs. 84, II., and 86); it consists of lobed 

 ciliated cells, and its lumen is always occluded, The ducts 

 leading from the funnel are much branched and intracellular, 

 they at length unite and open into a vesicle which leads to the 

 exterior (Fig. 85, II.). In Nephelis and Trocheta the funnel 

 lies in a hollow of the botryoidal tissue. It has recently been 

 maintained that the structures, usually ciliated and often oc- 

 cluded, which are found at the inner ends of the nephridia have 

 nothing to do with those organs, but may take some part in 

 maintaining the circulation of the blood. 



The nervous system consists of two cerebral ganglia 

 and a ventral chain, which in Hirvdo contains 23 ganglia 

 (Fig. 86). The cerebral ganglia give off nerves to three 

 minute ganglia which supply the jaws, and also nerves to the 

 eyes and goblet-shaped sense organs. A number of simple 

 eyes are found in the head in most forms ; in Fiscicola they are 

 also found in the posterior sucker. The ventral nerve-chain 

 lies in the ventral blood-sinus (Fig. 84, II.). 



Leeches are hermaphrodite ; the genital openings are ven- 

 tral, median, and unpaired, the male being in front of the 

 female. In Hirvdo there are nine pairs of testes, arranged in 

 segments 8 to 16 ; ia Nephelis the testes are numerous, and 

 scattered irregularly. They open into short transverse ducts, 

 which unite into a longitudinal vas deferens. Each of the latter 

 becomes coiled at its anterior end, forming an epididymis, and 

 the two unite to form a single short duct. This opens to the 

 exterior by a muscular protrusible penis, at the base of which 

 prostatic glands are usually found (Fig. 86). 



The true ovaries are filamentous bodies contained in 

 capsules. These capsules, iisually called the ovaries, occur in 

 Hirudo in the seventh segment, one on each side of the nerve 

 cord. The internal openings of the oviducts perforate the walls 



