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Studies were undertaken to discover the relative molecular distances separating some familiar forms of ciliated protozoa, and the genetic species they include. Sequences of 190 bases of the D2 domain of the large ribosomal nucleic acid molecule were obtained by polymerase chain reaction from protists of three distinctive groups of ciliated protozoa-Colpoda, Paramecium and Tetrahymena. Evolutionary trees were constructed for each set of sequences using the PHYLOGEN 1.0 string programs. All three groups of ciliates manifested large molecular diversity among strains difficult or impossible to distinguish morphologically. The largest single evolutionary distance within a group was the 75 differences separating Tetrahymena paravorax from the other tetrahymenids. The largest mean distance for a group was the 21.2 for the colpodids. In all the protist groups the large molecular diversity is obscured by morphological conservatism associated with constraints of ancient designs. The molecular diversity within morphotypes argues for long evolutionary coexistence of species differentiated from each other in significant physiological, ecological, or nutritional ways.

Cryptic species are common among protists and have long been known in ciliates. The ciliate genus Tetrahymena contains a large group of morphologically indistinguishable species referred to as the 'T. pyriformis' complex. These species include those reproductively isolated by mating type as well as asexual species characterized by the absence of the germinal micronucleus. This paper examines the molecular diversity of the species and describes the biogeography of 'T. pyriformis' species. Most species are globally distributed, though the best studied species, T. thermophila, is conWned to North America and gives evidence of population structure in local populations. Selfers and asexual species are common and arise from sexual species, a possible exploitation of nuclear dimorphism. It is argued that the cryptic species likely have diVerent ecological roles and that the biodiversity of Tetrahymena in particular, and ciliates in general, is underestimated. AbbreviationsCOX1 Cytochrome oxidase 1 subunit CT Connecticut D2 A hypervariable region of LSU FL Florida IL Illinois

Relation between RNA, DNA, and protein synthesis in the replicating nucleus of Euplotes. Proc. Nut. Acad. Sci. U. S. 47, 686-93. 26. Rao, M. V. N. 1964. Nuclear behavior of Euplotes woodrufi during conjugation. J . Protozool. 11, 296-304. 27. Raikov, I. B. 1960. Khromosomy v makronukleuse ravnoresnichnoi infuzorii Nassula ornata Ehrbg. Tsitologia (Moscow) 2, 598-601. 28. -1965. Chromosomal apparatus and ultrastructural peculiarities of the macronucleus of some Nassulidae (Ciliata, Holotricha). Progress in Protozoology, 94. 29. Roth, L. E. & Minick, 0. T. 1961. Electron microscopy of nuclear and cytoplasmic events during division in Tetrahymena pyriformis. J. Protozool. 8, 12-21. 30. Ruthmann, A. 1963. Die Strukture des Chromatins und die Verteilung der Ribonucleinsaure im Macronucleus von Loxophyllum meleagris. Arch. Protistenk 106, 422-36. 31. Seshachar, B. R. 1947. Chromatin elimination and the ciliate macronucleus. Amer. Nut. 81, 316-20. 32. -1963. The chromosomes in the ciliate macronucleus. XVI Intern. Congr. Zool. 2, 295. 33. -1964. Observations on the fine structure of the nuclear apparatus of Blepharisma intermedium Bhandary (Ciliata: Spirotricha). in Euplotes patella with special reference t o the nuclear phenomena. Uniw. Calif. 37. White, M. J. D. 1946. The cytology of the Cecidomyidae (Diptera) I. Polyploidy and polyteny in salivary gland cells of Lestodiplosis spp.SYNOPSIS. Gigantomonas usually exists in the multinucleate stage. Hence, multiple fission is more common than binary fission. In its flagellate as well as its aflagellate state it is always an amoeboid cell which possesses from one to several large, clear pseudopodia. Fairly often in the multinucleate, as well as the uninucleate, stage no extranuclear organelles are present except large plain centrioles, two of which are always closely associated with each nucleus. During nuclear reproduction four centrioles, two old ones and two new ones, are always present with each nucleus. During all nuclear reproductions, regardless of the number of nuclei present, extranuclear organelles, such as flagella, axostyle, undulating membrane, and costa when present are discarded. If they are renewed, it is by the new centrioles at the same time that the old ones produce new central spindles, two always cooperating in the process. Thus, Gigantomonas, like other genera of the Devescovinidae, the family to which it belongs, HE main purpose of this paper is, first, to show that