272 



PKOCKEDINGS OF .SECTION D. 



2.— TEEMATODE PARASITES AND THE RELATIONSHIPS AND 

 DISTRIBUTION OF THEIR HOSTS. 



By S. J. Johnston, B.A., D.Sc, Demonsirator of Biology, University 



of Sydney. 



Trematodes, and indeed other parasitic worms occur in fauna 

 groups. If we consider the trematodes living as parasites in some 

 particular class of host that dwells in a defined z«o-geographical region, 

 we must look for the nearest relatives of each of these worms, not in 

 host-animils of other classes living in the same region, but in hosts 

 of the same class living in different regions. For instance, the trematode 

 parasites of Australian frogs find their nearest relatives, not amongst 

 trematodes living in Australian reptiles or fishes or in any other 

 Australian animals, but living in frogs in Asia, Europe, and America. 

 A detailed study of all the trematode parasites living in frogs from all 

 the regions in which frogs occur, discovers some very interesting 

 circumstantial evidence concerning the origin, paths of dispersal and 

 relationships of these hosts ; the same may be said, of course, of other 

 classes of vertebrates serving as hosts. 



Trematodes have been collected from frogs in four definite zoo- 

 geographical regions ; and each region presents a group of frog-parasites 

 comparable to those from the other regions. This is very readily seen 

 when put down in tabular form ; in the following table the trematodes 

 parasitic in the frogs of the four regions referred to are put down side 

 by side. The European group is represented by the greatest number of 

 forms partly because it has been worked up more completely than the 

 other s;rout)s. 



European. 



Aujtr£ili?n. 



Pneumonaeces, 

 three species. 



Halipegus, 

 one specie^. 



Opisthioglyphc, 

 one species. 



In the Lungs. 



Sub.-fam. Haplometrinae. 



Pneumoncsces, I Pneumonoices, 

 sis species. j one species. 



In the Bdocal Cavity. 



Halipegus, I 

 one species. | 



In the Intestine. 



Sub,-Fam. Plagiorchinse. 



Glypihelmins, Dolichosaccus, 



one species. three species. 



Bracliysaccus, 

 two species. 



Pneumonosces, 

 one species. 



Hailpegus, 

 one species. 



