THE OPALINID CILTATE IXFUSOrJA^'S. 353 



American in their origin (except O. vlrgula in a Polypedates (?), 

 from Ceylon) and are a northern group and Opalina virgula may 

 have been derived independently from Cepedea^ as noted above. 

 ''Opalina ohtrigona has migrated to Asia and Europe (in Hyla ar- 

 horea)^ but is still confined to the North Temperate Zone. Of the 

 broad Opalinas in the Eastern Hemisphere (fig. 255) all are north 

 temperate forms except one species from Siamese Cambodia {0. 

 rotunda in Rana erythroea) ^ one species from Java {O. japonica (?) 

 in Bona limnocharis) ^ and three species from tropical Africa {0. 

 camerunensis in Hylamhates^ a Randid, 0. natalensis in Phryiioha- 

 trachus, a Sudanese Ranid, and an unnamed species from Rana rrms- 

 careniensis) . Of the species and subspecies of Opalina, whose 

 locality is known, 28 narrow forms and 10 broad forms are northern 

 and 5 wide forms are southern. This statement omits 6 forms inter- 

 mediate in shape, all northern, and it includes Central American and 

 West Indian forms as northern, for they evidently came from the 

 north. Opalina virgula also is omitted from consideration. The 

 distribution of the Opalinae, both narrow and broad, seems to in- 

 dicate they are northern in origin as well as in present habitat. 



How did the African species of Opalinae latae reach their present 

 home? They did not come from South America, for no Opalinas 

 of any sort are known from South America. They must have 

 reached Africa from Euro- Asia in the late Tertiary (fig. 237, p. 305) 

 or in the Pleistocene (fig. 238), a migration corresponding in time 

 and route to that of Bufo and Rana, in one or both of which hosts the 

 Opallnae probably entered tropical Africa. 



The presence of a narrow Opalina (sp. ?) in a Cuban Hyla (sep- 

 fentrionalis) is of much interest. It indicates the persistence of the 

 Antilles-Central American bridge until after broad Opalinas had 

 reached America from Asia, had there met Hyla and in Hyla had 

 been changed into the narrow form. On geological evidence 

 Vaughan (1919) puts the two Central America-Antilles bridges in 

 the Pliocene. This would agree with the distribution data. 

 ■ The Ranidae and Bufomdae are families with an abundant devel- 

 opment in the northern regions of both hemispheres. Their charac- 

 teristic parasites are Protoopalina, Cepedea and both broad and nar- 

 row forms of Opalina. The eastern frogs and toads have the broad 

 Opalinae, the western frogs and toads have chiefly the narrow Opali- 

 nae, but show some species which grade toward the broad forms. 

 Especially anterior daughter cells, after fission, are broad and may 

 show no trace of a pointed posterior end. These might readily be 

 mistaken for individuals of the ranarum-like group. On the other 

 hand, some of the forms of 0. ranarum itself, and of other species of 

 its group, are somewhat narrow posteriorly, but the actual posterior 



