160 J. B. CLELAND AND T. H. JOHNSTON. 



Tasmanian bred animals. As mentioned above, one of ns 

 has recorded the presence of the nodules in cattle in 

 Western Australia. 



Considering that the mammals of Australia are all mar- 

 supials, with the exception of Canis dingo, a few rodents, 

 bats, and sea animals such as whales, seals, etc. and there 

 are no indigenous bovines, it seems reasonable to suppose 

 that these parasitic worms were introduced along with 

 bovines or allied ungulates at one time or another. The 

 alternative view is that the worm's natural host is one of 

 the indigenous animals mentioned above, and that its 

 occurrence in cattle is more or less accidental. This would 

 pn-uppose that the iilaria in question could develop to a 

 great extent, if not entirely, in a new host removed by a 

 large phylogenetic interval from its normal host, a con- 

 dition unlikely to occur in such specialised parasites. 1 

 Further, in no indigenous Australian animal has any para- 

 site been so far encountered resembling the one in question. 

 The first hypothesis, therefore seems by far the most 

 rational to adopt, and may be stated as follows:— Filavia 

 (fiUsoni is an introduction from outside of Australia, having 

 accompanied its true host with the importation of the 

 latter. This true host is either some variety of domestic 

 cattle or the buffalo now so prevalent in parts of Northern 

 Australia or possibly a more distantly related ruminant 

 such as the camel or some other ungulate such as the horse. 

 It further follows that these parasites almost certainly do 

 still exist in their original hosts in the country from which 

 these came and will be found there on systematic search. 



It may be of value to review here the sources from which 

 Australian cattle, ImUaioi-s and camels have been derived, 



