NO. 8 PARASITES — METCALF 1$ 



was not so much to prove certain particular taxonomic, zoogeographi- 

 cal and paleogeographical propositions as to illustrate and emphasize 

 the method of using parasite data in the study of such problems. 

 That, indeed, is the chief purpose of the present paper also. 



Metcalf studied the opalinid parasites found in the preserved Anura 

 (frogs and toads) in the United States National Museum, including 

 species from all parts of the world. He was already familiar with 

 those occurring in Europe. Other species were obtained from the 

 Indian Museum at Calcutta and a few more from South America. 

 Assuming the general correctness of a set of Mesozoic and Tertiary 

 maps compiled by himself, chiefly from Arldt, von Ihering, Scharfif 

 and Schuchert, and based upon geological and biogeographical evi- 

 dence, not including parasites, he studied conjointly the taxonomy 

 and distribution of the xA^nura and their opalinid parasites and applied 

 these data from biogeography, paleogeography and from the host- 

 parasite studies, to problems of the place and time of origin of differ- 

 ent hosts and groups of hosts, of different parasites and groups of 

 parasites, to the routes, times and directions of dispersal of both hosts 

 and parasites, and in the discussion pointed out evidence bearing on the 

 correctness of the maps used, and upon problems of ancient climates. 



Before applying the data from the study of the opalinid parasites 

 he tabulated the available data from both hosts and parasites under 

 six items as follows : " Species of opalinid ; Host species ; Family 

 or subfamily of host ; Known geographical occurrence of opalinid 

 in the species of host named ; Known occurrence of host ; Known 

 occurrence of genus of host." This tabulation, used in connection 

 with maps of the present day oceans and of the continents in the 

 several geologic periods, was of great aid in studying present and 

 former distribution of both hosts and parasites, places and times of 

 origin of each and routes and directions of dispersal. The publication 

 of similar tables may properly be urged upon those zvho undertake 

 comprehcnsiz'e studies of any group of parasites. They will make 

 the author's data most easily available to other students and so should 

 extend the general use of host-parasite data. Where data from fossils 

 of either hosts or parasites are known and are sufficiently extensive 

 they should be tabulated, say under such items as these : Geographic 

 locality of fossils of the host family ; Geologic period of such fossils ; 

 and, if fossil remains of the parasites are known, similar data as to 

 them should be tabulated. Of course preservation of parasites as 

 fossils will be rare, but their spoor may be found and may be quite 

 specific, as, for example, in the case of the Peridermiums of pines. 



