606 Mr. R. J. Ortlepp on a new 
dorsal and ventral surfaces of the middle third of the seg- 
ment, in which ali the genital organs are confined. Dorso- 
ventral muscles were not observed. 
(b) Eacretory System.—The excretory system consists of 
two longitudinal vessels, dorsal and ventral, on either side 
towards the lateral margins of the segments. In the head 
region the corresponding vessels from each side unite and 
form a loop between the suckers. The ventral excretory 
vessels are large and thin-walled; they are more or less 
circular in transverse section, with a diameter of about 110 » 
in mature segments. In the hinder end of each segment a 
transverse duct, 25 in diameter, connects the ventral 
vessels. The dorsal excretory vessels are much smaller, but 
Fig. 3. 
Transverse section of portion of mature segment, reconstructed 
from serial sections. 
C.P.=cirrus-pouch ; D.Z.C.=dorsal excretory canal; Z.M,=longitudinal 
musele-layer ; N.C.=nerve-cord; Ov,=ovary; R.S.=recepta- 
culum seminis; S.G.=shell- eland; 7'.=testis; 7.M.=transverse 
muscle-layer; Vag.=Vagina; V.D.=vas deferens; .L.C.= 
ventral excretory canal; J”.G.=yolk-gland. 
have a thicker and slightly muscular wall; they are situated 
at about the level of the dorsal margin of the ventral vessel, 
but more towards the interior of the segment. In transverse 
section they are circular with a diameter of 15. Like the 
ventral vessels they also are connected to each other by 
transverse vessels, situated one at the hinder end of each 
segment, and running parallel to, but dorsal of, those con- 
necting the ventral vessels. Towards the posterior end of 
the strobila the lumen of the dorsal vessels may increase in 
diameter, so that in ripe segments they may attain about 
half the diameter of the ventral vessels. 
(c) Nervous System.—The nervous system consists of two 
well-developed lateral nerve-trunks. In general, the poral 
