
568 RECORDS OF THE S.A. MusEUM 
Sporoeysts taken from the liver of ZL, lessond infeeted with C. lesson were 
similar, but were present in far greater numbers as the latter snail is many times 
larger than P. isingi, and is subject to very heavy infestations with this parasite. 
METACERCARTA, 
Attempts have been made to infeet with C, lessoni, the fish Gambusia affinis 
and Carassius auratus; tadpoles (Limnodynastes sp. aud Hyla peront) ; molluses 
(Amerianna spp., Limnaca lessoni, Planorbis isingt); the yabby (Cherar des- 
tructor); and mosquito Jarvae. None of these attempts was suecessful, On 
two separate occasions, about six weeks apart, two leeches (Glossiphonia sp.) 
were both exposed to fairly heavy infections; seven weeks after the second 
exposure the leeches were dissected. Poth eontained a large number of thick- 
walled cysts, of two sizes, embedded in the tissues of the body wall. As the 
leeches used had been taken from the River Murray, and had thus been exposed 
to the possibility of natural infection, the results of the experimental infeetion 
are open to question; but the occurrence of the eysts in two sizes, corresponding 
with the two infections, and the large number recovered, indicate that they were 
the result of experimental infection. The same sort of eysts were recovered from 
a similar leech exposed to infection with verearia from the other host, Limnaca 
lessoni. 
The cysts (fig. 8) are thick-walled and slightly egg-shaped. The measurements 
(in micra) of a cyst of the smaller size, are as tollows: length of cyst, 299; breadth 
of cyst, 246; length of cavity of cyst, 205; breadth of cavity, 180, Measurements 
of a cyst of the larger size are; length of eyst, 893; breadth, 328; length of cavity, 
278; breadth 246. 
The thickness of the cyst wall made the exeystment of the living metacercaria 
unfeasible by ordinary mechanieal methods; so a solution of pepsin in 0-4 p.c. 
hydrochloric acid, warmed slightly, was used to dissolve the cyst wall and liberate 
the metacercaria, Although this ensured that undamaged metacercariae were 
obtained, none remained alive Jong enough to faeihtate stidy of the exeretory 
system, so that only the grosser features were seen (fig. 7). Purther study was 
made using preserved specimens, stained with neutral red and examined in 
a serum mount, or stained with Delafield’s haematoxylin and examined in methyl 
salicylate mounts. 
The metacerearia is a Tetracotyle, fairly active in life, especially when 
warmed slightly, as in the process of dissolving the cyst. In a cyst under cover- 
slip, most of the anatomical features of the larva ean be seen, although the pro- 
portions of the body cannot be determined (fig. 10). In an exeysted metacerearia 
