Evolution of Starfishes: Morphology, Molecules, Development, and Paleobiology. Introduction to the Symposium

Among starfishes, fascinating life cycles and complex morphologicalpatterns have evolved within a familiar but unusual basic bodyplan. In spite of these rich complexities, available phylogeneticinterpretations conflict, and the history of this importantgroup remains uncertain. The symposium brought together currentperspectives on phylogeny, the implications of certain poorlyknown aspects of asteroid morphology, and consideration of significantevents that preceded the diversification of extant asteroidgroups in the Mesozoic. It has become axiomatic in modern organismal biology that stronglysupported phylogenetic reconstructions are crucial to the understandingof biological pattern and progress. Although asteroids exhibitcomplex morphologies, life cycles, and behaviors that indicatetheir status as ideal model organisms in the study of marineinvertebrates, their evolutionary history remains obscure. Thisis in part due to a lack of treatment by researchers but alsoin part due to inherent limitations of the available data. In the following pages, the state of inquiry into the studyof relationships among starfishes is arranged in three sections:the nature of the fossil record (an introduction to modern starfishes),taxa and morphology, and phylogenetic interpretations.     

Growth and Development of the Banana Plant: 3. A. The Origin of the Inflorescence and the Development of the Flowers: B. The Structure and Development of the Fruit

In this paper, which is presented in two parts, the growth anddevelopment of the banana plant have been examined from thestandpoint of the origin of the inflorescence and the developmentof the flowers (Part A) and the structure and development ofthe fruit (Part B). First the main centres of growth in thesestructures are located and the manner of their development ispresented. Thereafter, attention is focused upon the salientevents which determine the alternative courses of developmentwith a view to designating the chemical and physiological stimulithat may be required.