Ref ID : 2037
O.W. Heal; Morphological variation in certain Testacea (Protozoa: Rhizopoda). Arch.Protistenk.Bd. 106:351-368, 1963
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The taxonomy of Testacea is based almost entirely on the size, shape and structure of the test. Although Jennings (1916) produced considerable variation in clones of Difflugia corona by artificial selection, little attention has been paid to variation by many workers describing new species to Testacea. Wailes pointed out that "Varietal and specific names have frequently been assigned to apparently distinct varieties which subsequent investigation has shown to be connected with each other by an unbroken series of slight modification" (Cash, Wailes and Hopkinson 1919). Some morphometric studies have been made to assess the validity of various species (Hoogenraad and De Groot 1937, 1952; Bartos 1938; Decloitre 1954; Ertl, 1954; Chardez 1956; Grospietsch 1957; Stepanek and Juri 1958) but it is necessary to obtain more information about the causes of variation and Stepanek (1952) has found that in Difflugia and Lesquereusia the structure of the test depends largely on the nature of the substratum. During a survey of the Testacea of bogs and fens (Heal 1961) specimens belonging to the Nebela tincta-collaris-bohemica group were found to occur in a wide range of habitats and showed much size variation. This group has provided considerable taxonomic difficulties since it was recognized by Leidy in 1879. A detailed examination was therefore made of this group on material from Vallery Bog in the Moor House National Nature Reserve (Nat. Grid Ref. NY761330), where a pool-hummock Sphagnum complex provided a series of habitats (Heal 1961).