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The concern of this stndy has been the chemical composition of Uaphnia omgnu, the algae (Selenustrum, cnpricornutuni, Ankistrodesmus convolutus) it was fed, the two growth media in which the algae were cultured and the water (Lake Huron, Michigan, USA) in which D. magnu was reared. A synthetic diet (fish chow+alfalfa) was used as a control. The effectiveness of these five diets on the health of the 1). inagna populations was ascertained by t,he weight and number of neonates thus produced. The diet, S. capricornufuin cultured in an organic medium, prodnced the largest mean brood size and the heaviest neonates in unstressed populations. The synthetic diet prodnced the smallest mean brocd size and the lightest neonates. Stressed organisms may produce smaller broods wit.h heavier neonates than unstressed organisms. The erolnticnary significance of this observation is discussed. Statistical studies suggetit that daphnids maintained on the synthetic diet derired no demonstrable nutritive value from the diet in terms of elemental composition or amino acid production. A great similarity in patterns cf amino acid quantity and type was noted in the algae and the daphnids. On further examination it was discoverctl that this pattern was widespread in other aquatic forms, bacteria, fungi, yeasts, casein and was common t o a variety of birds and mammals. It may be suggested that products that are made and stored, such as lipids. are less uniform in pattern among widely diverse species than those that have t o he produced and are not stored. such as amino acids.

The application of atomic absorption spectroscopy to the analysis of magnesium alloys and scrap aluminum is described. Ca, Cu, Mn, and Zn are determined in Mg alloys, while Cu, Fe, Mg, and Zn in the alloy range are determined in the aluminum samples. In aluminum analysis, synthetic standards and a spiking procedure are employed to compensate for matrix effects. Comparison with chemical results shows AA (atomic absorption) to be a reliable analytical tool in these applications.