CHAETOPODA 149 
which are very constant in position, being with hardly an ex- 
ception in the 13th segment. In Hudrilus (Fig. 94) the ovary 
is enclosed in a muscular sheath. The ciliated oviduct passes 
through the sheath, and ends in a funnel-shaped mouth in the 
ovary. The muscular sheaths of the oviduct and ovary are 
Fie. 94.—Female reproductive apparatus of Eu- 
drilus. On the right side the spermatheca has 
been cut away to show the contorted oviduct, 4. 
1. Ovary. 2. Spermatheca. 
3. Gland opening into conjoined duct of sper- 
matheca and oviduct. After Beddard. 
4. Oviduct. 
continuous. The oviduct is convoluted, and opens to the ex- 
terior on the 14th segment, together with a spermatheca and 
a small glandular body. The opening of the oviduct in Peri- 
Fic. 95. —Diagrams of various earth- 
worms to illustrate external char- 
acters. A, B, C, anterior segments 
from the ventral surface. D, 
hinder end of body of Urochaeta. 
A. Lumbricus; 9 and 10, segments 
contain spermathecae, the ori- 
fices of which are indicated ; 
14, segment bears oviducal 
pores ; 15, segment bears male 
pores; 32, 37, first and last 
segments of the clitellum. 
B. Acanthodrilus ; 1, orifice of sper- 
mathecae ; ? , oviducal pores ; 
3, male pores, 
C, Perichaeta; the spermathecal pores 
are between segments 6 and 7, 
7 and 8, and 8 and 9, the ovi- 
ducal pore on the 14th, the male 
pores on the 18th segment. 
In all the figures the nephridial 
pores are indicated by dots, the setae 
by strokes. 
chaeta 1s single and median. The various positions of the 
genital apertures, and their relations to the nephridia and setae 
in various genera, are shown in Fig. 95. In the aquatic 
Oligochaets the nephridia are not found in those segments 
which lodge the reproductive organs and their ducts; in 
the terrestrial forms they coexist. Some of the setae in the 
