HIRUDINEA 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, Sranchellion and Piscicola 
probably possess a similar nephridial network. 
Clepsine and Hirudo have paired nephridia distinct from 
one another. The funnel in Hirudo lies in the same blood 
sinus as the testis (Figs. 84, IL, 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 Mephelis 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 Hirudo contains 23 gangha 
(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 Piscicola they are 
also found in the posterior sucker. The ventral nerve-chain 
lies in the ventral blood-sinus (Fig. 84, IT.). 
Leeches are hermaphrodite; the genital openings are ven- 
tral, median, and unpaired, the male being in front of the 
female. In Hirudo there are nine pairs of testes, arranged in 
segments 8 to 16; in Nephelis the testes are numerous, and 
seattered 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, usually 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 
