192 Transactions of the Royal Society of South Africa. 
moment, and one notices that the fluid has already taken effect by the 
opacity of the tissues round the edges. The weights are replaced, and 
finally removed after a period varying from five minutes to half an hour,, 
according to the bulk of the worm. 
The worms are further left in the fixing fluid for fifteen minutes and 
longer. They are subsequently washed in 40-50 per cent, alcohol, left for 
a day or so in iodised 70 per cent, alcohol, and they are then ready for the 
after treatment of staining and mounting. 
I also obtained very good results by using 10 per cent, formalin as a 
fixative for whole mounts. 
The following trematodes, referred to their systematic position, have 
been found : — 
Order HETEEOCOTYLEA Mont. 
Family POLYSTOMIDAE Taschbg. 
Sub-family Polystominae Van Ben. 
Genus Polystomum Zeder. 
1. Polystomum integerrimum (Rud.) Frol.? 
In 1758 Roesel von Eosenhof (21) first figured and described this trema- 
tode from the urinary bladder of the frog without apparently naming it. 
In 1792 M. Braun (6) found it in the bladder of the green frog Rana esculenta 
(L.), and described it as Planaria uniculata, n. sp. 
Zeder (25) in the year 1800 first attempted a classification of the then 
known trematodes. The various helminthologists had previously often 
described and figured the same animal under different names. The genus 
name Planaria, to cite one instance, was in turn used to denote entirely 
different worms. Zeder founded the genus Poly stoma, and referred the 
above-mentioned Polystomum integerrimum to this genus as Polystoma ranae. 
Rudolphi (22) was the first to describe and figure it under the name by 
which we now know it, viz. Polystomum integerrimum (he, however, wrote 
it Polystoma integerrimum). 
Von Baer and Van Beneden (1827), Stieda and Willemoes-Suhm all sub- 
sequently contributed to its anatomy and development. It was, however, 
left to Zeller (26), who first in 1872 and afterwards in 1876 gave a complete 
description and fully worked out the life-history of this parasite. 
Polystomum integerrimum is found in the urinary bladder of Xenopus 
laevis from Stellenbosch. About 5 per cent, of these frogs, popularly 
known as " platanas," harbour this parasite. I observed from one to 
six in the urinary bladder. Curiously enough, I never came across it in a 
large number of Rana fuscigula from Stellenbosch, Paarl, and Worcester. 
