TREMATODA. 779 



From the stomach the tailless larvae succeed in entering 

 the common liver duct and its branches, in which situa- 

 tion they rapidly acquire all those internal organs which 

 characterise the adult flukes. In this way the life cycle 

 is completed. 



From the researches of Van Beneden, and especially also of 

 Pagenstecher, it would further appear that the degree of multi- 

 plication of the larvae and the extent of their organization are 

 largely affected by varying states of the season, in association 

 with other co-ordinating external conditions. This conclusion 

 is important practically. For example, the highly organized 

 germ-sacs or sporocysts (redice) are capable, under favourable 

 climatal states, of developing not only the ordinary tailed cer- 

 cariae in their interior, but also new germ-sacs ? It would seem, 

 further, that there is no recognisable limit either to the variety 

 or to the extent of larval fluke development. Ko wonder, there- 

 fore, that an accidental concurrence of favourable conditions, 

 such as happens in particular seasons, should be followed by the 

 disastrous outbreaks recognised as epidemics of rot. As we 

 cannot regulate the character of the seasons, so neither can 

 we prevent the occurrence of many epizootics. Helminthological 

 science, however, does enable us to lessen the amount of disease, 

 by affording an adequate insight into the nature of the causes 

 concerned in its production. We may, indeed, yet be able to 

 ascertain with precision what intermediary bearers are imme- 

 mediately concerned in the harbouring of the cercarean or pupal 

 representatives of the common fluke ; and should these guests 

 be found to reside in the body of some one particular and 

 readily accessible mollusc, it is obvious that the collection and 

 destruction of the intermediary bearer in question would operate 

 to limit, if it did not, in course of time, altogether serve to 

 eradicate the disease. 



Guided by indications of the order just mentioned. Dr. Eowe, 

 of Mount Battery, Goulburn District, Victoria, has proposed a 

 somewhat rough and ready method of stamping out the rot, 

 which disease, by tlie way, appears to be far more constant as 

 an epizootic in Australia than it is with ourselves. In brief, 

 the plan suggested was to burn the whole of the grass where 



