Haswett—A Monograph of the Temnocephalee. 123 
There are in all the species two pairs of testes, both laterally situated about midway 
between the dorsal and the ventral surfaces. Both testes are more or less oval in 

shape, with the long axes nearly parallel with the long axis of the body—the anterior 
somewhat more produced in 7. fasczata and ZT. minor than in the rest. In the two 
last-named forms and in 7. Dendyi both pairs are imperfectly divided externally by a 
series of slight constrictions or depressions corresponding to the series of transverse 
bands of the parenchyma muscle (vzde Plate xiv. fig. 1). In the rest the testes are 
completely undivided. They are coinpletely invested by a thin fibrous layer, which 
is, in great part at least, muscular. From the posterior end of the anterior testis 
there runs back a narrow efferent duct, which is continuous behind with the posterior 
testis. The true vas deferens arises from the posterior testis, and the spermatozoa 
from the anterior testis must pass through the substance of the posterior. Both 
efferent duct and vas deferens are lined by a very thin continuation of the fibrous 
investment of the glands. 
The two vasa deferentia unite at a point to the left of the median line, in front of 
the genital opening into a large oval or pyriform sac—the vesicula seminalis (Bly xan 
noise kx he.21): Pl xiv. fig 2 and) Pl xv. figs. 1 and 3, v. s.). In the 
terminal part of the vas deferens, which is more dilated than the rest, there is a 
distinct protoplasmic layer, not divided into cells, and with nuclei at long intervals, 
internal to the fibrous investment, and both those layers are continued in the wall of 
the vesicula seminalis. The lumen of the vesicula seminalis is nearly always full of 
spermatozoa, which exhibit slow, coiling, streaming movements. 
In certain of the species —7. minor, T. Dendyt, T. comes, T. Senyperi—there 1s 
on the left side of the seminal vesicle opposite the base of the cirrus a coecal pouch 
(e. s.), which, in the Australian forms mentioned, is of considerable size, club-shaped, 
somewhat curved. In 7. fasczata it is scarcely constricted off from the bulb-like base 
of the cirrus. In 7. Sener? it is described and figured by Weber* as a short rounded 
sac. Weber describes it as “ gland-like,” but the structure of its wall is precisely the 
same as in the case of the vesicula seminalis—-with an external muscular investment 
and an internal protoplasmic layer, without cell-outlines, and with a very small 
number of prominent nuclei. It usually contains a small number of actively-moving 
spermatozoa; and as the contraction of its walls was observed repeatedly to be 
followed by the protrusion of the penis and sometimes by the discharge of seminal 
matter from the extremity of the latter, it may be most appropriately named 
ejaculatory sac. 
The cirrus, or penis, is a tubular organ, continuous with the ejaculatory sac and 
vesicula seminalis. It lies always on the left side and is directed obliquely inwards 
* Weber, /.c. Taf. 1. fig. 1, p. 13. Semper gives a similar account of it and terms it prostate. 
