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Updated: May 7, 2025
In the second case the entire development of the progenitors is also passed through by the descendants, and, therefore, so far as the production of a species depends upon this second mode of progress, the historical development of the species will be mirrored in its developmental history.
As to formations without the requisite gemmules. Mr. Lewes and Professor Delpino. Difficulty as to developmental force of gemmules. As to their spontaneous fission. Pangenesis and Vitalism. Paradoxical reality. Pangenesis scarcely superior to anterior hypotheses. Buffon. Owen. Herbert Spencer. "Gemmules" as mysterious as "physiological units." Conclusion.
Having regard to this general scheme of geological knowledge and thought, it is obvious that geological speculation may be, so to speak, anatomical and developmental speculation, so far as it relates to points of stratigraphical arrangement which are out of reach of direct observation; or, it may be physiological speculation, so far as it relates to undetermined problems relative to the activities of the earth; or, it may be distributional speculation, if it deals with modifications of the earth's place in space; or, finally, it will be ætiological speculation, if it attempts to deduce the history of the world, as a whole, from the known properties of the matter of the earth, in the conditions in which the earth has been placed.
Then the dorsal furrow, characteristic of the Vertebrate, appears the brain, the organs of the senses; at a later period are formed the intestine, the limbs, and the permanent form of the respiratory organs, from which the class is recognised with certainty. "Consequently the high importance of developmental history is indubitable.
On account of this developmental change, he doubted if the cholera organism should be ranked with bacilli; it is rather a transitional form between the bacillus and the spirillum. Possibly it is a true spirillum, portions of which appear in the comma shape, much as in other spirilla e. g., spirilla undula, which do not always form complete spirals, but consist only of more or less curved rods.
Nor, again, does it depend upon sameness of form or fashion; for personality is felt to survive frequent and radical modification of structure, as in the case of caterpillars and other insects. Mr. The plastic force has changed its mode of operation. These are due to a new and distinct developmental process."
The subjects of his experiments have been various species of sea-urchins, but the principles discovered will doubtless be found to apply to most, or perhaps all, forms of vertebrate life as well. While these studies were under way another developmental problem was being attacked in a neighboring room of the laboratory by Professor Kitasato, of the University of Tokio, Japan.
Bronn, who translated Darwin’s works into German, was and remained loyal to the idea of a “developmental law”—that there is within the organism an innate tendency towards self-differentiation and progress, thus a purely teleological principle.
Sloyd at its best tries to correlate several series, viz., exercises, tools, drawing, and models. Each must be progressive, so that every new step in each series involves a new and next developmental step in all the others, and all together, it is claimed, fit the order and degree of development of each power appealed to in the child.
You might define the life of every one in exactly the same terms as those which I have now used; the difference between the highest and the lowest being simply in the complexity of the developmental changes, the variety of the structural forms, the diversity of the physiological functions which are exerted by each.
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