350 ON .SOME TRKMATODE PAHASITES OF AUSTRALIAN FFJOfiS, 



1'iniuin, in the bladder of frogs, does not seem to be represented 

 ill America in frogs, but three species (P. coronatnm Leidy, P. 

 hassalli Goto, and P. ob/ongnm R. Wright) occur tlierc in tlie 

 bladders of CheIonimis\ wliile in AustraHa, this heterocotylean 

 genus is represented by one species in the bladder of frogs. No 

 representatives of Diplodixcus nor Pnli/stomum have 3'et been 

 described from Asia. The American Cephahxjdiiiniiin aniericaiius, 

 in the intestine of frogs, may be represented in the Old World by 

 C. lenoiri Poir. The genus Ganeo, described by Klein from the 

 Indian Rana hexadarfi/laiSS), seems to stand alone, unrepresented 

 in any other region. 



Tt is a remarkable fact that, of the six species of flukes described 

 from frogs inhabiting southern Asia, four of them appear to find 

 their nearest relatives in flukes from Australian frogs. Mesoece- 

 liit,m sociale Liihe, is certainly more closely related to the Austra- 

 lian species of Mesocmliuvi than to Brachycfelium crassicolle R., 

 its European, or B. hospifale Staff., its American representative. 

 Pneumotueces ccvpyristes Klein, has been shown above(Section iv.) 

 to be moi-e nearly related to P. australis than to any other of the 

 European or American species of this genus; and the Asiatic 

 Pleurogenes gastroporas and P. tiphrrrictis, and the Australian P. 

 freycineti and P. solus have likewise been shown to be more 

 nearly related to one another than any of them are to the Ameri- 

 can or European pleurogenetines. 



T think the Asiatic frog-flukes, so far as they are known, are 

 more nearly related to the European than are the Australian, 

 standing, as it were, intermediate between the two latter groups. 

 Tlie American frog-flukes, on the other hand, many of which 

 have evolved into distinct genera, are not so nearly related in 

 their structure to the European as are the Asiatic. And, in 

 addition to this, the American genera, generally speaking, con- 

 tain more species than the same genera in Asia and Australia, 

 and this may be taken to indicate that the American frogs, with 

 their flukes, liave been longer separated from the parent-stock. 



The great similarity of the four groups of flukes of frogs found in 

 the four regions mentioned, points to the fact, I think, that the 

 rtuk(^s are a very old group of animals, and existed in the ances- 



