312 
Distonia liiteiim n. sp. etc. 
course of the enquiry, viz., a large somewhat flat cercaria with a bifurcate 
tail, a cercaria with eyes (both found also in Physa), and a small cercaria, 
with a comparatively long tail provided with numerous bristles, found 
in a small snail, Tomichia ventricosa. 
It may point to something worthy of further attention that, though 
in America and other countries the fluke is abundant, the intermediate 
host does not seem to have been determined with complete certainty. 
Several molluscs are suspected as the probable host, yet it should appar¬ 
ently be easy to demonstrate this. In Australia it is of interest to note 
that the intermediate host of the liver-fluke is believed to be a species 
of Physa, in which rediae and cercariae were found resembling those 
of the liver-fluke, but that the same difficulty was encountered as in 
South Africa in finding the encysted stage, though this was not regarded 
as a serious objection to accepting the rediae and cercariae as those of 
the fluke. 
Renewed attempts to And the missing intermediate stage in C. comma 
resulted in the discovery that the cercariae, after swimming about 
freely, returned again to a snail, entered by the nephridial opening and 
became encysted in the region of the pericardium. Obviously the other 
host therefore was some animal that lived on the snails. The numerous 
frogs, which inhabited the same water in which this snail occurs, were 
suspected, and experiments showed conclusively that they were re¬ 
sponsible for the adult fluke of this cercaria. This fluke is abundant in 
the alimentary canal of frogs, and is closely allied to Distoma echinatum 
Zeder., but, as its life history shows, it is a different species and may 
be called D. luteum from its characteristic colour. 
The facility with which all the stages of this fluke can be found 
renders it a useful type for students of zoology in South Africa. 
Search was then made elsewhere for the intermediate stages of the 
liver-fluke. At one time the sheep on certain lands at the Agricultural 
College at Stellenbosch were badly infected with fluke. No sheep were 
in consequence allowed on these grounds, and no signs of the disease 
were subsequently found in the locality. Physa tropica occurred in 
abundance here but on dissection did not reveal any rediae or cercariae. 
There had been no cases of the disease for several years here, but I was 
informed by Mr C. P. Lounsbury that a case of fluke in a horse had 
occurred not far off at a place, Koelenhof, a few miles distant. This 
place we visited and specimens of the ubiquitous tropicaweve readily 
procured, but no other fresh-water snaih Nothing new was expected 
from these, but specimens were collected in a tube, in which shortly 
