The Plecoptera community of a small stream in Oregon,U.S.A. *

The Plecoptera community of a small woodland stream in Oregon was studied by examining density and species composition. Four sites were studied using benthos sampling for larvae and emergence trap collections for adults. Sixteen genera and forty-three species were identified with most species occurring in relatively low numbers. A comparison with the species list from an earlier study suggested that the species composition has not changed markedly in 40 years but there were several changes in relative abundance. Species diversity of stoneflies decreased with distance from the headwaters. These changes were correlated with decrease in habitat complexity, decrease in stability of the substrate, and increase in water depth. Examples of longitudinal succession are given as a method enabling the large number of species to partition the habitat. Concurrent benthos and emergence sampling demonstrated differences in emergence success that were correlated with habitat suitability.     

An Investigation of Antibiotic and Drug Residues in Fish

The use of antibiotics and drugs in fish farming has prompted an investigation into the elimination of these residues from fish muscle. Young rainbow trout were given intraperitoneal injections of either chloramphenicol, framycetin, oxytetracycline or sulphadiazine/ trimethoprim and muscle tissue was examined by microbiological assay over a period of weeks for the presence of active residues. The effect of the method of administration of two of the drugs was also investigated and the results discussed.     

The molluscan spermatozoon: Dynamic aspects of its structure and function

The morphology of "primitive" and "modified" sperm types inmolluscs is reviewed. The cytochemical localizations of glycogenreserves and enzymes related to the metabolism of glyocogenare discussed in relation to their roles in sperm motility andthe iiltrastructure of the mid-piece of molluscan spermatozoa.     

Voluntary Associations in History

Formal common interest associations appear to have become prominent during the neolithic, but to have declined subsequently in preindustrial nations. The industrial revolution supported a new proliferation. With this, the mode of operation changed: associations came to unite on the basis of rational-legal sanctions. Modern voluntary associations may contribute to social stability as adaptive mechanisms for traditional institutions. They may socialize and support individuals caught in the disorder of social change.