202 ANNULATA. 
anterior end are specially contractile and form the /aeral 
hearts. The dorsal vessel is also contractile. 
The drain lies in the prostomium, with a xerve-ring 
ee round the pharynx and a double nerve-chain 
"along the ventral surface. The nerve-chain has 
double ganglia in each segment. 
The xephridia are numerous, a pair occurring in nearly 
every segment. They are complex coiled tubes with an 
eeretory. internal funnel, a coiled excretory part and a 
* small bladder or vesicle leading to the exterior. 
The funnel always opens into the coelomic compartment in 
front of the one in which the bulk of the nephridium lies. 
Fig. 128.—A NEPHRIDIUM OF LUMBRICUS. 
Nephrostome. 
\ 
a B 
8 we 
4 " § 
2 j g 
First 4 s 
Thine & 
walled 
Portion. First 
Thin- 
walled 
Second Portion. 
‘Loop. 
Third So Te SE Pies 
Muscular Sai PR og — ple Sag . 
Portion. External 
SRR Aperture. 
Respiration appears to be carried on by the skin. The 
worm is hermaphrodite. The male organs consist of two 
pairs of ¢es¢es lying in the roth and r1th seg- 
ments. They are enveloped in the large branch- 
ing seminal vesicles, from each of which there passes a vas 
deferens backwards to open on the 15th segment. The 
pair of ovaries lie in the 13th segment, and the ov¢ducts, with 
funnels opening into the same segment, run through the 
septum and open to the exterior on the 14th segment. 
Two pairs of sfermathece or small spherical sacs open 
between 9 and 10 and between 10 and 11 on each side. 
The eggs are laid in cocoons and undergo an embryonic 
development. The cocoons are secreted by the clitellum. 
Reproductive. 
