Evolution of Castes in Insects l BERNHARD RENSCH The evolution of organisms in the succession of generations has been primarilly achieved through the appearance of new hereditary variants with minor deviations along with the development of stable structures and functions. Harmful mutants were eradicated either immediately or in the subsequent generations through the process of natural selection while unharmful or advantageous ones usually survived. As this process continued, many new races and species developed which possessed structures and functions of a rational nature and which became increasingly independent from their environment. These evolutionary tendencies were also promoted through either geographical, ecological, physiological or genetical isolation of populations. In some phylogenetic lines, there occurred an increase in the number of cells due to additional cellular divisions in the morphogenesis of structures. This opened up the possibility for the development of the division of labour within cellular groups leading to more complicated and consequently more successful functions of tissues and organs. A further advancement in the adaptation of a species to its environment was made possible through specialization for certain functions of whole individuals or groups of individuals.

New essays by outstanding European and American medievalists on major aspects of the most enduring medieval epic. The legend of Tristan and Isolde -- the archetypal narrative about the turbulent effects of all-consuming, passionate love -- achieved its most complete and profound rendering in the German poet Gottfried von Strassburg's verse romance Tristan (ca. 1200-1210). Along with his great literary rival Wolfram von Eschenbach and his versatile predecessor Hartmann von Aue, Gottfried is considered one of three greatest poets produced by medieval Germany, andover the centuries his Tristan has lost none of its ability to attract with the beauty of its poetry and to challenge -- if not provoke -- with its sympathetic depiction of adulterous love. The essays, written by a dozen leading Gottfried specialists in Europe and North America, provide definitive treatments of significant aspects of this most important and challenging high medieval version of the Tristan legend. They examine aspects of Gottfried'sunparalleled narrative artistry; the important connections between Gottfried's Tristan and the socio-cultural situation in which it was composed; and the reception of Gottfried's challenging romance both by later poets inthe Middle Ages and by nineteenth- and twentieth-century authors, composers, and artists -- particularly Richard Wagner. The volume also contains new interpretations of significant figures, episodes, and elements (Riwalin and Blanscheflur, Isolde of the White Hands, the Love Potion, the performance of love, the female figures) in Gottfried's revolutionary romance, which provocatively elevates a sexual, human love to a summum bonum. Will Hasty is Professor of German at the University of Florida. He is the editor of Companion to Wolfram's "Parzival," (Camden House, 1999). Click here to view the introduction (PDF file 83KB)