THE VICTORIAN NATURALIST. 123 



INTERMEDIATE HOSTS OF THE LIVER FLUKE. 



It is interesting to note that the early stages in the hfe-history of 

 the Liver Fluke are now being worked at by some of the members 

 of the Club. 



On a recent excursion to Heidelberg (nth January) specimens 

 of the freshwater snail, BuUnus tenuistriatus, were obtained, 

 and from some of these the Rev. W. Fielder and Mr. Howard 

 Cummins obtained large numbers of the larval stages known as 

 redia and cercaria, similar in form to those reported from the 

 European intermediate host, Limncea truncatula, and at the 

 ordinary monthly meeting (r3th January) living specimens were 

 exhibited of these stages. 



A few days later, whilst working through some of the material 

 from the Heidelberg ponds, Mr. W. J. O'Neill found quantities of 

 the larval stages in a snail of the genus Planorbis, whilst Mr. 

 Fielder also noted in the same kind of snail the larval stages 

 of a distinct variety, the redice being of comparatively large 

 size and the cercarice possessing a forked tail. This may be 

 only a modification of the common fluke larva. It, however, 

 occurs by itself, and not in company with the ordinary form. 

 Another variety of cercaria, different in many particulars from 

 the typical form, also occurs in Planorbis, but up to the present 

 it has not been met with in sufficient numbers to allow of 

 extended observations. 



Mr. Fielder further reports the presence of fluke in the snail 

 Bulinus injlatus, as also in Ancylus Australicus, a limpet-like 

 form of very minute size. What causes surprise is the 

 wonderful amount of ingenuity which the ciliated embryo 

 fluke employs in obtaining admission to the pulmonary 

 chamber of such snails as Planorbis and Ancylus. The 

 former takes the shape of a disc only -^l in. thick and }i in. 

 across, whilst the latter can scarcely measure half that size. 

 Our special climatic conditions evidently arouse desire in the 

 embryo to widen its choice in the matter of suitable hosts. This 

 fact unfortunately multiplies the chances of the increase of 

 fluke, for whilst only one species of one genus favours the trans- 

 miss on of the pest in Europe, at least three or four different 

 genera must be credited to Australia. 



The special point of interest, however, in connection with the 

 recent discoveries is that as regards the date of the encystment of 

 the cercaria:-, as at this stage the larval flukes become dangerous 

 if eaten by sheep. It is asserted that in European countries the 

 cyst is taken into the sheep whilst they are feeding upon grass or 

 weed which has been submerged during the embryo life of the 

 fluke, and left dry later in the season. What Mr. Fielder has 

 observed, however, is a number of cysts loithin the snails Planorbis 

 and Ancylus — forms so small that they can easily be swallowed by 



