. Studies in general physiology. Physiology; Phototropism; Geotropism; Reproduction; Irritability; Regeneration (Biology). 334 Studies in General Physiology cell-membrane, and that it certainly has no relation to the orientation of the first cleavage plane. For when we first allow the eggs to develop in ordinary sea-water into the two- cell stage before bringing them into dilute sea-water, it can be noticed that the first cleavage plane may lie in any posi- tion with regard to the point of rup- ture; the material lying nearest the rupture will be that which flows out. Figs. 91—94 are drawings
. Studies in general physiology. Physiology; Phototropism; Geotropism; Reproduction; Irritability; Regeneration (Biology). 334 Studies in General Physiology cell-membrane, and that it certainly has no relation to the orientation of the first cleavage plane. For when we first allow the eggs to develop in ordinary sea-water into the two- cell stage before bringing them into dilute sea-water, it can be noticed that the first cleavage plane may lie in any posi- tion with regard to the point of rup- ture; the material lying nearest the rupture will be that which flows out. Figs. 91—94 are drawings of eggs the membranes of which were made to rupture in the two-cell stage, and which illustrate what has been said FIG. 91 more clearly than words. Since the extraovate develops in all cases, if it is only sufficiently large, we must conclude that, so far as the question of divisibility is concerned, the protoplasm must be considered an isotropic substance. 9. What conceptions can we form of the nature of the smallest elements of living matter which are capable of development? As Nussbaum has shown, every attempt that has been made of assuming as the ulti- mate elements of living matter some- thing analogous to the atom and the molecule has failed, for the simple rea- son that two different substances, nucleus and protoplasm, are necessary. One might assume that a combination of two different "micellse"—one composed of nuclear material, the other of proto- fi'^- 82 plasm—might represent the smallest living element. Our experiments show that such an idea would be entirely wrong, when full capacity for development is taken as the criterion of living matter, inasmuch as a very considerable quantity of substance is necessary for full development—an amount Digitized by Microsoft®. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perf
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