Ophthalmidium: A study of Nomenclature, Variation, and Evolution in the Foraminifera

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Abstract
Summary: Some variable foraminifera from the base of the Upper Lias at Byfield, Northamptonshire, have been used as evidence supporting completely opposed "evolutionary series" based on the "law" of recapitulation and its converse, proterogenesis. The authors obtained closely spaced samples of this foraminiferal clay and studied them in order to establish the actual succession of forms. The first major portion of the paper (section III), a complicated discussion of nomenclature, is necessary in order to give a name to the forms studied. Here a number of genera and species are established or redefined. The following section (IV) attempts to establish the bounds of the species by means of a detailed variation study. It is found possible to define closely the species studied; though they are highly variable, no transition from one species to another is seen. Finally, in section V it is shown that the actual succession of forms does not support the theory of proterogenesis, but rather that of recapitulation. A marked shift of the mode of variation is observed within a time interval represented by the deposition of 2 feet of clay. The contribution which the variation study can make to systematics is also discussed.