466 PROCEEDINGS OF THE NATIONAL MUSEUM vol.87 



the origin of each group of these hosts; the routes and the geologic 

 times of the distribution of several groups of hosts; the places and 

 times of origin of the several genera and some of the subgenera of 

 opalinids and the routes and times of their distribution. Paleogeo- 

 graphic hypotheses of Arldt, Haug, Scharff, Schuchert, and others 

 are tested by using them in connection with the distributional data 

 from Anura and opalinids and seeing whether the hypotheses furnish 

 reasonable explanations of the faunal data. The methods of specia- 

 tion in the opalinids and the general principles of their evolution also 

 are discussed. 



ACKNOWLEDGMENTS 



I have received invaluable assistance of various sorts from many 

 sources during the course of these studies. Many institutions have 

 contributed to the work: The Johns Hopkins University, before I 

 was elected to the faculty, welcomed me for a year to its department 

 of zoology and for another year to its school of hygiene; the United 

 States National Museum gave permission to gather opalinids from its 

 anuran collections. Dr. Leonhard Stejneger aided with many sugges- 

 tions, and Miss Doris Cochran assisted by identification of species, 

 especially of tadpoles from India and Burma; Prof. T. N. Annandale 

 and the Indian Museum at Culcutta sent numerous Indian Anura, as 

 also did the Colombo and Madras Museums; the National Academy 

 of Sciences helped, with a grant of money and with introductions, 

 toward a half-year trip to South America for collecting and study, 

 and for this trip Prof. Vernon Kellogg, executive secretary of the 

 National Research Council, Dr. C. D. Walcott, secretary of the 

 Smithsonian Institution, and Dr. Leo S. Howe, director general of 

 the Pan American Union, gave most helpful introductions ; the Oswaldo 

 Cruz Institute, especially Prof. Adolpho Lutz, Miss Bertha Lutz, and 

 Dr. Gualter A. Lutz, obtained for me fine collections of living Anura 

 from Rio de Janeiro and several neighboring Brazihan states and 

 furnished me luxurious laboratory faciUties; the Institute of Hygiene 

 and Public Health of the University of Montevideo rendered similar 

 service; the Marine Biological Laboratory of Woods Hole, Mass., 

 furnished much material, including a large series of tadpoles of Rana 

 clamitans in all stages of development; the Zoological Museum at 

 Ann Arbor, Mich., through the kindness of Prof. A. G. Ruthven and 

 Mrs. Helen T. Gaige, gave a complete series of larvae of Ascaphus 

 truei; Prof. C. E. McClung and Dr. C. L. Parmenter, of the University 

 of Pennsylvania, proffered the hospitality of their vivarium for 

 about two years to a hundred or more specimens of Bombina igneus 

 and B. pachypus, though unfortunately the fire toads did not breed. 



Many individuals also have helped greatly with material or data 

 or both: Prof, W. A. Haswell and the late Prof. Launcelot Harrison 



