THE OPALINID CILIATE INFUSORIANS. 469 



JSlalaysian and Australian species. The three Cepedeae all belong to 

 one subgeneric group confined to Africa and Madagascar except for 

 one species in Florida, which seems related, though not very closely 

 so. The three Opalinae, all of course broad, are probably compara- 

 tively recent immigrants from Euro-Asia and show little of special 

 interest. 



Two Cepedeae and one Opalina are known from the islands which 

 are remnants of formerly more extensive Indian Ocean lands uniting 

 southern Africa with India. Madagascar and the Seychelles Islands 

 each furnish a single species of Cepedea^ the two very similar and 

 very closely related to a western African species. Ceylon has a 

 strange Opalina of narrow form, but probably not related to the 

 Opalinae angustae of North America. 



The general indications from this regional survey are in agree- 

 ment with the conclusions and suggestions already made in the body 

 of this volume, except that the greater abundance of the species of 

 ZelleneTla in Central America (11), the Antilles (4), and northern 

 South America (9) than in southern South America (6) seems to 

 cast doubt upon the origin of this genus in Argentina-Patagonia, as 

 we have proposed. The Leptodactylidae, which are doubtless the 

 original hosts of the Zelleriellas, show about an equal number of 

 species in the two contrasted regions, thought the area of the more 

 northern region is many times the greater. There are also in the 

 northern region a far greater variety of hosts for ZeTleriella to adopt. 

 On the whole there seems no sufficient ground for changing our 

 suggestion of a southern origin for the Leptodactylidae and their 

 ZeTleriella parasites. 



A few words further may well be added as to the origin of the 

 Hylidae. AVe have suggested that this family arose in the highlands 

 of eastern Brazil, north of the sea which separated Patagonia-Argen- 

 tina from tropical America. The Hylidae and Leptodactylidae seem 

 very closely related, and the two families probably arose in adjacent 

 regions and from common ancestors. If the Leptodactylidae arose in 

 southern South America, then the Brazilian highlands is the most 

 probable place of origin for the Hylidae. Again, if the Hylidae had 

 arisen further north, in any region connected with the eastern Pacific 

 land strip while this was complete from Ecuador to Asia, it seems 

 inexplicable that the Hylidae should not have extensively colonized 

 Asia as they have North America. It seems that the South American 

 home of the Hylidae was united to Australasia, but not to Asia, 

 since the time of the origin of tlie Hylids, except for the compara- 

 tively modern connection between South America and Siberia by way 

 of the Isthmus of Panama and North America. 



