14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8l 



and their trematodes, accepted this judgment of Johnston's. Harrison 

 questions this conclusion and predicts *' with the utmost confidence " 

 that future additions to the then very scant knowledge of Asiatic frog 

 trematodes (six species) and the Trematoda of Australian frogs will 

 show " that .... the closest affinities of Australian frog trematodes 

 .... lie with those of South American frogs." In this 191 3 paper 

 Johnston refers to trematodes of AustraHan sea eagles, sea gulls and 

 herons and he points out also that two flukes of the genus Harmosto- 

 mimi found in two Australian marsupials are so closely related to 

 another Harinostoinuiii from a South American opossum that they 

 " must be considered as derived from common ancestors." Johnston 

 must have had in mind the bearing of these parasite data upon prob- 

 lems of former connection of Australia with Asia and with South 

 America, but neither in this nor in two subsequent papers ( 1914. 

 1 916) upon Australian trematodes and cestodes in general did he 

 bring out clearly the paleogeographic importance of his data. He 

 emphasized chiefly their bearing upon the genetic relationships between 

 the hosts. 



Metcalf, the author of the present paper, was the fourth student 

 of parasites to come independently to a 'realization of the important 

 aid which parasites may give in solving proljlems outside the field 

 of parasitology proper, and he used the host-parasite method in his 

 earlier papers ' much more extensively than it had been used before ; 

 but really he added nothing essential to the conception of this method 

 which von Ihering had in 1891 and 1902. Kellogg too seems to have 

 realized the applicability of the host-parasite method to other problems 

 than genetic relationships of hosts, though he made but scant, if any, 

 application of it to them. Harrison carried Kellogg's work upon bird 

 relationships further and also in his papers subsequent to 1924 used 

 parasite data extensively in problems of zoogeography and paleogeog- 

 raph}'. Priority is of very little interest, but, for what it is worth in 

 this matter, the priority is clearly von Ihering's. 



Metcalf in his chief paper (1923) purposely overemphasized his 

 data, endeavoring to bring out even slight suggestions which could not 

 be established without corroboration from other sources.^ His desire 



^ Seven papers from 1920 to 1924; also one in 1928. 



^ " The endeavor will rather be to present the known data from the Anura and 

 the Opalinidae and note their implications. Even very scant data, insufficient to 

 have any real weight as they stand, will be stated and their implications noted, 

 with the thought tliat even very minor items, of slight moment by themselves, 

 may sometime be correlated with other data and then be of interest. The 

 endeavor is, therefore, to have the treatment of this theme inclusive rather than 

 critical." (From Metcalf, 1923.) 



