556 PROCEEDINGS OF THE NATIONAL MUSEUM vol.87 



female gametes, which fuse and grow to adult opalinids. One can 

 imagine possible infection of a termite from cysts deposited by an 

 anuran with its feces in, say, a hollow log, and the continued infection 

 of termite from termite in the new environment by means of cysts in 

 the feces. But before this is accepted it must be much better indi- 

 cated than it now is, the presence in two termites of forms doubtfully 

 resembling Opalina being all that we have to go upon. 



THE GROWTH OF OPALINA VIRGULOIDEA METCALF IN THE 

 TADPOLES OF RANA SYLVATICA LECONTE 



By Margaret Cowles and Maynard M. Metcalf 



The Opalina of the American wood frog was named virguloidea 

 by Metcalf (1923a). In the same publication he described a species, 

 0. larvarum, from the common green frog (Rana clamitans) and 

 suggested that this very broad, orbicular opalinid belonged to the 

 subgeneric group Opalinae angustae rather than to the Opalinae latae, 

 this proposed classification based on the presence of a minute curved 

 posterior point, now known to be sometimes found also in broad 

 Opalinas. At that time late stages in the life history had not been 

 seen. Material secured later showed that this guess, though based 

 on a mistaken assumption, was correct, for the tadpoles ready for 

 metamorphosis, with four legs present, though with the tail not yet 

 absorbed, show Opalinas of narrow form. 



On the basis of observations upon the development of Opalina 

 larvarum in the tadpoles of Rana clamitans and of a similar species 

 in the tadpoles of Rana catesbeiana, Metcalf reported in 1925 to the 

 National Academy of Sciences that the Opalinae angustae pass through 

 a series of larval stages recapitulating the evolution of the family 

 Opalinidae. The Opalinae angustae are the most highly evolved 

 members of the family, and it was found that their larval stages are, 

 first, Protoopalina-like, then Cepedea-like, that then the Cepedea 

 larvae flattened, first in front and then throughout the length of the 

 body, becoming broad Opalinae, and that before metamorphosis 

 these broad Opalinae changed to narrow forms. No drav/ings were 

 published with this report, but charts of the phenomena in Opalina 

 larvarum were shown to the American Society of Zoologists in Cleve- 

 land, Ohio, during the Christmas holidays in 1930. It was also 

 reported that Zelleriella passes through a Protoopalina stage, Cepedea 

 through a Protoopalina stage, the Opalinae latae through a Protoopalina 

 stage followed by a Cepedea stage, and the Opalinae angustae through 

 three larval stages, representing, first, Protoopalina, then Cepedea, 

 then the Opalinae latae, finally assuming their definitive narrow form. 

 It has seemed worth while to review here this remarkable life history 

 for another narrow species of the genus Opalina and to give dra^vings 

 of the larval stages in their sequence. 



