What help may we de- rive, then, from the embryologists who have made the greatest progress in this respect? The Editors, on the other hand, must bear the responsibility for the plan and the scope of the book, and assume the blame for any defects in its structure. A Note on the Proportion of Injured Individuals in a Natural Group of Bufo. His personality may have made him think as he did; but it was the eagerness of his contemporaries for oversystematization, in terms of just such abstractions as his, that was responsible for the success of his doc- 18 Problems, Concepts and Their History trine. Surrounding the skeletogenic micromeres are cells of the veg2 lineage, shown in green in. Stuttgart, Franckh'scher Verlag, 8°, 48 pp.
Totton ; assisted by H. Inhibition of the membrane potential change also does not block the decompartmentalization of intracellular K nor the increase in permeability to K. With an English translation by A. Except for the shared repeat sequence element, both the repetitive and single copy regions of the members of each set of clones failed to crossreact. Sexual Phenomena in the Free-living Nematodes.
When he demonstrated that animal organs — the in- testine and probably the central nervous sys- tem — are formed by the folding of homoge- neous layers into tubes he called them by the name for leaf. Nevies aus dem Leben unserer Erde Sonnencultus und Bedeutung der Sonne als Lebensquelle. In embryology, too, as we have seen, the concept developed before the technique to verify or refute it. Embryos of the echinoderms, especially those of sea urchins and sea stars, have been studied as model organisms for over 100 years. But his conceptions of the wider Universe, based on pure reason, because statically and struc- turally interpreted and thus transmitted by medieval commentators, deluded posterity, and it was unfortunately the static Aristotle, the Aristotle of a sterile cosmogony, crystal clear but crystal rigid, who dominated the thought of the Middle Ages. Frank, associate editor, Charles D.
Only those ex- periments should be presented that are crucial and analytically strong and convincing. Defect present at first appearance of optic ve- sicles. Here again we have to consider the regulatory state of the target genes in the two mutually excluded domains and in the rest of the embryo as well. Biochemical tests show that certain of the properties of the particulates may be retained after isolation. In color by Harold J.
Combinations of Alternative and Blending Inheritance. Although the differing isolating mechanisms of vicariance and rapidly evolving gamete recognition proteins have been proposed, a stable and robust phylogeny is unavailable. His con- temporaries were going far to cry physical facts to fit a philosophical pattern. The mechanisms ensuring the regulation and programming are, evidently, basically different, as a regulatory apparatus must respond to a systems deviation from a given parameter, whereas the program implies alteration of the parameters in time. Reish 1969 466R 1694 Biology of the seas of the U. And Roux' experimental pro- gram, carried to its logical outcome bv the addition of the transplantation methods, in a way implied by it, has led straight to the modern embryology which incorporates the valid features of both epigenetic and pre- formationistic concepts. The possible significance of the results is discussed.
If a primary obligation of the embryolo- gist, before he can evaluate an experimental result, is the knowing of the normal condi- tion of the embryo, the fundamental paradox arises that he cannot perhaps adequately know the normal without the benefit of the experiment, whose whole raison d'etre can surely be only that it elvicidates the normal; yet he cannot interpret his experimental re- sult without comparison with the normal control. Morphology and Biochemistry of Diploid and Androgenetic Haploid Merogonic Hybrids. William Croone on generation; in Studies and Essays in the History of Science and Learning Offered in Homage to George Sar- ton on the Occasion of his Sixtieth Birthday 31 August 1944, edited by M. Vor Allem spielen die Kriimmungen und Faltungen in dieser Schneider-Theorie die wich- stigste Rolle. To come to the vertebrate, which we are in the habit of con- sidering more conventional and stable em- bryological material, Fundulus heteroclitus embryos raised at constant temperatures reach specific morphological stages after dif- ferent periods of time when raised at varying salinities Merriman, unpublished. Nuclear structures and nucleus-cytoplasm relations will be considered in another chapter and will therefore not be included in this presen- tation.
A Litter of Short-tailed Dogs. Ueber eine eigenartige Grenzzone in der Schleimhaut zwischen Muskelmagen und Duodenum beim Vogel. Contribution a 1' etude du peritoine des Pleuronectes. Nitecki ; with the editorial assistance of Doris V. This is a more than philosophical problem when experimentalists in Princeton, for instance, are comparing their results with those of investigators working at the Uni- versity of Chicago in an attempt to work out basic mechanisms of development. It is unthinkable that in anything kinetically as complex as the simplest protoplasm, alteration of its equili- bria by chemical or thermal changes could be limited in its effects to a single system alone.
Palade and Claude ignore the evidence that the Golgi material can be seen in the living cell. Rathke, in particular, whose quality of mind was in many ways like that of von Baer, made par- ticular advances in demonstrating the exis- tence of the germ layers in invertebrates as well as vertebrates and in discovering the presence of gill slits in the mammalian em- bryo. In the cells of the adult organism, regulation is predominant; in cell differentiation, a program prevails. The Biophysics of Cleavage and Cleavage of Geometrically Altered Cells. Both experiments were subject to critical errors, as we now know, and for both eggs both explanations are partially correct and partially inadequate.