148 ZOOLOGY, 
of the nephridial network. This extraordinary change of a 
nephridium into a salivary gland is paralleled in the Arthro- 
pod Peripatus, in which developement shows that the salivary 
glands are modified nephridia. 
Three giant fibres, consisting of a sheath with a clear con- 
tents, occur dorsal to the ventral nerve cord in nearly all 
Oligochaets. Connections have been recently traced between 
them and the nerve fibres. Their function was formerly 
thought to be solely for the purpose of support; hence they 
have been termed the newrochord, and have been compared 
with the notochord of the Chordata in their physiological 
action. 
The Oligochaets are hermaphrodite: in the CHAETOGASTRIDAE 
the spermatozoa develope in the coelom, in Lumbricus the 
Fig. 93.—Genital segments of 
Iumbricus (slightly altered 
from Howes’ Biological Atlas). 
The left side represents the 
immature, the right, the 
mature condition, so far as the 
male reproductive organs are 
concerned. After Beddard. 
1. Anterior pair of testes; the 
second pair are in the 
next segment. 
. Seminal vesicles. 
. Spermathecae. 
Vas deferens. 
Ovary. 
Oviduct. 
Receptacula ovorum. 
Nephridia. 
Nerve cord. 
IO OP oD 
Ser fe) 
testes become enclosed in special vesiculae seminales which 
are outgrowths from three of the septa (Fig. 93). In these 
vesiculae the spermatozoa mature. 
In the aquatic Oligochaets the ova ripen in the coelom 
or in an egg sac similar to the vesiculae seminales of Lum- 
bricus. 
The testes are usually four in number, but there may be 
only one pair, as in Geoscoler. There is a single pair of ovaries, 
