This volume is devoted principally to the theme of behavioral develop ment. The study of ontogeny has attracted some of the most bitter and protracted controversies in the whole field of ethology and psychology. This is partly because the arguments have reflected more general and continuing ideological battles about nature and nurture. In the opening essay, Oppenheim shows how these debates have recurred in much the same form over the last century. His chapter also brings out a more worrying feature of such argument. He demonstrates that authors who are well known for their strongly held partisan views have written in much more balanced ways than is usually admitted. Although the ex cluded middle is familiar enough in academic argument, the dynamic tensions actually present in developing systems may be particularly prone to polarize debate about what is actually happening. This point is elegantly explored by Oyama in her essay on her concept of maturation."

This volume is subtitled "Alternatives" because we wanted to devote at least a part of it to the alternative ways in which members of the same species behave in a given situation. Not so very long ago the supposition among many ethologists was that if one animal behaved in a particular way, then all other members of the same age and sex would do the same. Any differences in the ethogram between individuals were to be attributed to "normal biological variation. " Such thinking is less common nowadays after the discovery of dramatic differences between members of the same species which are of the same age and sex. Alternative modes of behavior, though now familiar, raise particularly interesting questions about current function, evolutionary history, and mechanism. Do the differences rep resent equally satisfactory solutions to a given problem? Are some of the solutions the best that those animals can do, given their body size and general condition? Is an alternative solution adopted because so many other individuals have taken the first? If so, do the frequencies reached at equilibrium depend on differential survival of genetically distinct types or do they result from decisions taken by individual animals? If the alternatives are induced during development, as are the castes of social insects, what is required for such triggering? The questions about alternative ways of behaving are addressed in some of the chapters in this volume."

One of the attractive features of the great classical ethologists was their readiness to ask different kinds of questions about behavior - and to do so without muddling the answers. Niko Tinbergen, for instance, was interested in the evolution of behavior. But he also had interests in the present-day sur vival value of a behavior pattern and in the mechanisms that control it from moment to moment. Broad as his interests were, he clearly separated out the problems and recognized that questions about the history, function, control, and development of behavior require distinct approaches - even though the answers to one type of question may aid in finding answers to another. The open-minded (and clear-headed) style of ethologists like Tinbergen was based on a recognition that there are diverse ways of usefully con ducting research on behavior. This consciousness has been partially sub merged in recent years by new waves of narrowly focused enthusiasm. For instance, the study of the behavior of whole animals without recourse to lower levels of analysis, and the treatment of sociobiological theories as ex planation for how individuals develop, has meant that the relatively fragile plants of neuroethology and behavioral ontogeny have almost disappeared under the flood."