614 PROCEEDINGS OF THE NATIONAL MUSEUM vol.87 



which the species of Opalinidae diverge from each other, see the 

 genus Zelleriella and the subgeneric group Opalinae angustae, both of 

 which we have regarded as comparatively modern. When once the 

 adaptations to parasitism had been secured, there is no indication, at 

 any point in the further development, of any speeding up of the proc- 

 esses of evolution. 



A REVIEW OF THE LITERATURE OF THE OPALINIDAE SINCE 1923 



In 1909 and 1923 I critically reviewed the literature of the Opa- 

 linidae. The present review is intended to bring the survey down to 

 date. First let us mention a few papers that were omitted from the 

 former reviews or received insufficient reference. 



In 1891, L. and L. Zoya discussed the fuchsinophile plastids (bio- 

 plasts) of Altmann, briefly describing those of Opalina ranarum. 



In 1904, Cobb, not mentioning the opalinids, used parasites to 

 indicate genetic relationships between organisms, much as I (Metcalf, 

 1928c) used opalinids in discussing paleogeography and geographic 

 distribution. Cobb's interesting paper should be mentioned in that 

 connection. 



In 1913, Poche, in discussing the taxonomy of Protozoa, mentions 

 that in opalinids the "generative and morphological nuclei" are not 

 separated. 



In 1916, Mavor discussed Myxidium lieberkiihni, a parasite of 

 European and American pikes, much as Kellogg discussed the malloph- 

 agous parasites of birds to indicate descent from a common ancestor. 

 This paper should have been mentioned in Metcalf, 1928a. 



Ghosh, 1918, reports three new (?) species of opalinids from India: 

 0. [Cepedea] scalpriformis, 0. plicata, and 0. triangularis. (With the 

 exception of the first, the descriptions are too scant to allow specific 

 identification.) 



Ghosh, 1920, discusses the cytology of Opalina [Cepedea] scalpriformis, 

 says it is abundant in winter, is comparatively rare at other seasons, 

 that its "chromosomes" [nucleoli] are six in number, that its length is 

 24-57^4, its greatest width 8-1 5/*. 



In 1920, Tonniges described the mitosis of Opalina ranarum, but it 

 was not until seven years later (Tonniges, 1927) that he published the 

 illustrations. 



A paper by Chatton and Perard, in 1921, refers briefly to the 

 Opalinidae and to the fact that their period of encystment corresponds 

 to the breeding period of their hosts as significant in connection with 

 the evolution of parasitism. It also mentions the absence of encyst- 

 ment in Opalina [Protoopalina] saturnalis, a rare condition among 

 parasitic ciliates. 



Two little notes by Metcalf (1922a and b) call attention to alcohohc 

 specimens of Anura as a source for reasonably well preserved opalinids 



