190 Transactions of the Royal Society of South Africa. 
or black, owing to pronounced superficial pigmentation. This pigment is 
more pronounced in and round the eye-spots ; it then extends forwards and 
backwards in heavy radiating streaks. In the young immature cerceriae 
the pigment is confined to the eye-spots a short distance behind the anterior 
sucker. The body of a mature cerceria is oval, -42 mm. long, and greatest 
breadth -25 mm. The tail is -5--6 mm. long. The anterior sucker is small and 
circular, with a diameter of -03 mm., and the larger posterior ventral sucker 
has a diameter of -09 mm. The mouth leads into a slightly elongated 
oesophagus which bifurcates at a point just behind the eye-spots to form 
the two short limbs of the forked intestine. The tail springs from the 
dorsal posterior margin of the body just round the exterior margin of the 
posterior sucker. 
The excretory system consists of two lateral trunks. Each main trunk 
starts anteriorly in the region of the eye-spots, runs downwards and out- 
wards, and suddenly turns inwards. Here each trunk gives off a branch ; 
the branches from each side meet to form a transverse trunk. The main 
trunks on each side now run outwards and backwards and join just in front 
of the posterior sucker. At the junction is a well-defined excretory pore, 
that opens on the dorsal surface. After the two trunks have joined they 
continue as a single tube down the tail bifurcating just before it reaches the 
distal extremity to open on each side through two minute pores. 
Cystogenous cells are scattered throughout the organism. These cells 
aggregate to form chains around and along the course of the vascular trunks 
when the cerceria becomes less active and begins to encyst itself. 
The cerceriae readily encyst themselves on the sides of the glass tube in 
which they may be collected, and on grass stems introduced into the tube. 
The tail is now cast off, the anterior and posterior extremities are drawn in 
under the body, and a small round black speck about -2 mm. in diameter is 
formed. Encystation is accompanied by the expulsion of a granular mass 
containing small dark rhabdite-like bodies. This granular mass hardens 
when exposed to the action of sun and air. Before encystation takes place 
the cerceriae crawl or wriggle up the grass stems for a short distance, and 
encyst just above the water-level. 
I have no hesitation in regarding the cerceriae described above as 
identical with Cawston's Cerceria frondosa (7), which he removed from 
Isidora schakoi Jickeli, from Potchefstroom (Tol.). It is also the same 
as Gilchrist (13) recorded. 
