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The amphipod, Hyalella azteca (Crustacea: Hyalellidae), occupies an ecologically diverse array of permanent freshwater habitats, including lakes with predatory fish and fishless ponds and marshes. In a survey of southeast Michigan habitats I found that two distinct Hyalella morphotypes exist in the area. One morphotype is smaller in adult body size, size at first reproduction, and produces smaller eggs than the other morphotype. The smaller morphotype coexists with fish predators, the larger morphotype is found in fishless habitats. I examined the potential role of disparate predation regimes in generating and maintaining life history variation found between Hyalella populations. I measured size-specific mortality in the field during two years in two focal populations that differed in morphotype. In a lake habitat (with fish), mortality risk generally increased with size, and adult mortality exceeded juvenile mortality. The opposite mortality pattern was observed in a nearby fishless marsh habitat. Size-selective predation by major predators in each habitat appeared to contribute importantly to overall mortality patterns. Life history characteristics of Hyalella were measured both on field-collected individuals and individuals reared in replicated predator-free artificial ponds. Field and artificial pond samples indicated that the lake Hyalella population has a smaller mean adult body size, smaller size at maturity, smaller egg size, and higher size-specific fecundity and reproductive investment than the marsh population. Observed differences in life history traits between populations are in close agreement with predictions derived from life history models addressing the evolution of reproductive allocation, size at maturity, and egg size. I also examined determinants of reproductive success in the two Hyalella populations. Female reproductive success (through fecundity) increased with body size in a similar fashion in both populations. Male reproductive success increased substantially with body size in both populations, but the increase was greater and more consistent between years for males in the marsh population. Gnathopod size influenced male reproductive success in both populations, but this influence depended on male body size. Relatively small males, but not larger males, experienced significant levels of sexual selection on gnathopod size in both populations.

Scope and Method of Study: This study examines the credit practices of clothing retailers in Stillwater, Oklahoma. It considers the importance of credit to the retailers, the types of programs offered, and their individual approaches to the role that credit should play in their respective retailing efforts. It also examines the effect of a potentially large college student clientele upon the credit programs at the subject stores. All data was collected by personally interviewing the manager of each store using a semi-structured questionnaire. The study is primarily of an exploratory nature which presents a broad survey of the overall credit operations and does not try to analyze any one area in depth. Also, no attempt is made to present a quantitative analysis of the success or efficiency of any of the credit operations.

The Florida Technological University four-component strain-gage balance is an internally mounted, half-inch diameter balance capable of measuring four components of load: front and rear normal force, axial force, and rolling moment. Measurement of these components is accomplished by means of sixteen strain gages that are mounted on the balance and wired into four full bridge circuits. When the balance is subjected to a load, the strain gages, through a small resistance change, indicated the strain a balance element is undergoing. This report presents a description of the balance and its support equipment, and outlines specific calibration procedures necessary to their successful implementation. These calibration procedures take two forms: that of calibrating the readout equipment, and that of calibrating the balance itself. Also contained in this report is a method of reducing calibration data into a set of parameters applicable to the balance. To aid in the calibration of the balance, a calibration assembly was designed and built. Two calibration models were designed to facilitate the incremental loading of the balance and the interpretation of the readout data.