Brackish-water Polyclads. 187 
but contains a number of such cells as contain at base numerous homogeneous 
spherules stainable with eosin. 
Nervous System (PL VIII, fig. 4).— In this species the nervous system conforms 
closely to the type found in Polyclads generally. The brain (br), situated slightly in 
front of the pharynx, is enclosed in a tough capsule, and is of a kidney-Hke shape 
consisting of right and left halves divided by a shallow depression. Anteriorly each 
half is provided with a heap of ganglionic cells, usually known as Lang's " Korner- 
haufe" (kli), from which numerous sensory nerves arise. On the ventral side the 
brain gives rise to six pairs (an. In', In*, In*, In*, pn) of main nerve trunks, of which 
the last two branch repeatedly and anastomose, bringing about a network extending 
over nearly the entire ventral side of the body. The remaining nerve trunks also 
send out some anastomosing branches and finally join the marginal nerve-plexus. 
Male Genital Organs (PI. VIII, figs, i, 2, 5). — The testes are situated ventrally in 
the body. Ductules proceeding directly from them can not be brought under obser- 
vation. The seminal canals (sc), running backwards along the sides of the hind parts 
of the main gut, somewhat widen in part and thus serve as accessory seminal vesicles. 
Posteriorly they gradually narrow and unite into an unpaired median duct, the 
ejaculatory duct (ed), at a point far in front of the male aperture ( d" ). A true seminal 
vesicle does not exist. The ejaculatory duct proceeds obhquely backward and up- 
ward for some little distance and bends sharply round, finally to open at the tip of 
penis. At the base of penis, it receives the duct of the prostate from the dorsal 
side. 
The prostatic duct gradually widens anteriorly and passes over into the prostate 
proper (pr), which represents an elongate tube running forward in a wavy manner and 
ending blindly considerably in front of the junction point of seminal canals, much as 
in Echinoplana celerrima Haswell ' . The prostate is internally lined with a non- 
ciliated epithelium and externally invested with a wall of parenchyma including 
numerous muscular fibres. In its interior there usually exists a quantity of a finely 
granular secretion. 
The penis (p), which is entirely destitute of a stylet or any other special chiti- 
nous structure, is a small and bluntly conical body, projecting from above vertically 
into the antrum musculinum. This opens directly to the exterior by the male genital 
aperture, nearly on the anterior border of the last tenth of body. 
Female Genital Organs. — ^As usual the ovaries are dorsally situated, and though 
there exists an anastomosing system of fine ducts connecting them to the uterine 
canal, it is difficult to follow this out. The uteri (u), after running closely along the 
pharyngeal pocket on both sides, unite with each other and form the unpaired uterine 
duct (uu) in the neighbourhood of the hind end of the main gut ; the duct soon joins 
the median egg-canal (ec). From this junction point the egg-canal extends poste- 
riorly to the point of its origin by union of the two accessory vesicles (av) which, lying 
one on either side of the median line, extend anteriorly up to the level a short 
' Haswell, W. A., 1907. " Observations on Australian Polyclads." Transact. Linn. Soc. London., 2. Sen, Vol. IX, 
PP- 475-478. 
