THE OPALINID CILIATE INFUSORIANS. 351 



But the data should also be scrutinized from the point of view of 

 geographical distribution (fig. 254.) The group of ohtrigona-\ike 

 species (straight or slightly bent, narrow forms) is represented, a, 

 in 3 species of Scaphiopus, a North American Pelobatid; h, in 4 

 species of Cho?'ophilus, an American Hylid; c, in 16 species of the 

 genus Hyla, 9 of them from North America, Ifrom Central America, 

 1 from Cuba, and 1 from Europe with its 2 subspecies extending into 

 all temperate Asia; d, in 2 Central American species of Agalychnis, 

 a genus of the family Hylidae; e, in one Phyllomedusa, a Mexican 

 Hylid ; /, in 9 Buf os all from Central America or North America ; g, 

 in 1 Grastrophrynid from southeastern United States; A, in =>* species 

 of Rana from Central America or North America ; there are also 5 

 other species from Central America and North America which are 

 intermediate forms, 3 intermediate between the ohtrigona group and 

 the virgula group, and 2 intermediate between the obtrigona group 

 and the ranarum group. We thus see that the ohtrigona-VikQ, species 

 are exclusively Central American and North American, except for 

 the one species 0. obtrigona which has passed from North America 

 into Asia and across into Europe, being carried by Hyla arhorea, 

 the only species of Hyla found in Asia and Europe, except for two 

 " closely related " forms in eastern Asia, and an Abyssinian species 

 of doubtful relationship. 



The virgula-likQ species are not very different from the ohtHgona- 

 like forms, and there are four intermediate species. The only 

 marked difference is the strongly curved body. Virgula-like species 

 are known, a from three Hylas, all from western North America ; &, 

 from two Eanas, one from the eastern part, the other from the 

 western part of the United States; c, from Polypedates (?) macu- 

 Jatus from Ceylon — a most surprising occurrence which needs care- 

 ful scrutiny. Excepting Opdlina virgula itself, the Ceylonese form, 

 the virgul<i-\\kQ species are so similar to ohtrigona-like species in 

 structure and distribution that they may be treated together as one 

 group. Opalina virgula, on the other hand, is demarcated by its 

 long, slender, rod-like, endoplasmic plastids. I am inclined to be- 

 lieve it should be regarded as distinct in origin from the other 

 Opalinae angustae, and that it probably arose independently from 

 some Cepedea. We should have fuller Icnowledge of Indian ma- 

 terial. Removing Opalina virgula, then, from the other narrow 

 Opalinae, we may say that all the latter are Western Hemisphere 

 species, except that 0. obtrigona has secondarily invaded northern 

 Asia and Europe by way of Alaska. Note that though we find 

 in Australia Anura belonging to the same families whose members 

 in America harbor slender Opalinas. the Australian members of 



**■ O. [lawarurn] seems to be a narrow Opalina, but Its adult condition has not been seen. 



