Analysis of coelom development in the sea urchin Holopneustes purpurescens yielding a deuterostome body plan

An analysis of early coelom development in the echinoid Holopneustes purpurescens yields a deuterostome body plan that explains the disparity between the pentameral plan of echinoderms and the bilateral plans of chordates and hemichordates, the three major phyla of the monophyletic deuterostomes. The analysis shows an early separation into a medial hydrocoele and lateral coelomic mesoderm with an enteric channel between them before the hydrocoele forms the pentameral plan of five primary podia. The deuterostome body plan thus has a single axial or medial coelom and a pair of lateral coeloms, all surrounding an enteric channel, the gut channel. Applied to the phyla, the medial coelom is the hydrocoele in echinoderms, the notochord in chordates and the proboscis coelom in hemichordates: the lateral coeloms are the coelomic mesoderm in echinoderms, the paraxial mesoderm in chordates and the lateral coeloms in hemichordates. The plan fits frog and chick development and the echinoderm fossil record, and predicts genes involved in coelomogenesis as the source of deuterostome macroevolution

A hexamer origin of the echinoderms' five rays

Of the major deuterostome groups, the echinoderms with their multiple forms and complex development are arguably the most mysterious. Although larval echinoderms are bilaterally symmetric, the adult body seems to abandon the larval body plan and to develop independently a new structure with different symmetries. The prevalent pentamer structure, the asymmetry of Loven's rule and the variable location of the periproct and madrepore present enormous difficulties in homologizing structures across the major clades, despite the excellent fossil record. This irregularity in body forms seems to place echinoderms outside the other deuterostomes. Here I propose that the predominant five-ray structure is derived from a hexamer structure that is grounded directly in the structure of the bilaterally symmetric larva. This hypothesis implies that the adult echinoderm body can be derived directly from the larval bilateral symmetry and thus firmly ranks even the adult echinoderms among the bilaterians. In order to test the hypothesis rigorously, a model is developed in which one ray is missing between rays IV-V (Loven's schema) or rays C-D (Carpenter's schema). The model is used to make predictions, which are tested and verified for the process of metamorphosis and for the morphology of recent and fossil forms. The theory provides fundamental insight into the M-plane and the Ubisch', Loven's and Carpenter's planes and generalizes them for all echinoderms. The theory also makes robust predictions about the evolution of the pentamer structure and its developmental basis. *** including corrections (see footnotes) ***Comment: 10 pages, 6 figure

Winged men and the cast of dice: Anti-finalism and radical materialism in Guillaume Lamy

The controversy over teleology raged in the early modern period with particular intensity. In this paper, I will show that Guillaume Lamy represents a “radical” current of antifi nalism, devoid of weakness, and far from compromise with his adversaries. This antifi nalism makes of Lamy not so much a sincere supporter of the unknowability of God’s ends, as scholars have maintained — in other words, a proto– fi deist — but rather a radical Lucretian materialist, whose aim is to openly distance himself equally from the partial Cartesia

Nicole Bonnet, Immanence et transcendance chez Teilhard de Chardin, 1982

Cuénot Claude. Nicole Bonnet, Immanence et transcendance chez Teilhard de Chardin, 1982. In: Revue des Sciences Religieuses, tome 62, fascicule 1, 1988. p. 83

Teilhard de Chardin (Pierre), Lettres à Jeanne Mortier, 1984

Cuénot Claude. Teilhard de Chardin (Pierre), Lettres à Jeanne Mortier, 1984. In: Revue des Sciences Religieuses, tome 59, fascicule 3-4, 1985. pp. 280-281