. The dynamics of living matter . 194 DYNAMICS OF LIVING MATTER In these deformed eggs the distribution of the nuclear material during cell division is entirely different from that which normally occurs; yet normal embryos result. Driesch has shown the same in a different way; namely, by submitting the developing eggs to pressure. In eggs thus flattened, the planes of segmentation differ from those of the normal egg, yet normal embryos are formed. These observations exclude the idea that the distribution of the nuclear material through the egg is of importance for the form of the embryo. Dries
. The dynamics of living matter . 194 DYNAMICS OF LIVING MATTER In these deformed eggs the distribution of the nuclear material during cell division is entirely different from that which normally occurs; yet normal embryos result. Driesch has shown the same in a different way; namely, by submitting the developing eggs to pressure. In eggs thus flattened, the planes of segmentation differ from those of the normal egg, yet normal embryos are formed. These observations exclude the idea that the distribution of the nuclear material through the egg is of importance for the form of the embryo. Driesch succeeded in causing fertilized sea urchins' eggs to fuse in a number of cases. Such a fusion of the masses of two fertilized eggs into one, resulted in the formation of a sin- gle giant embryo (pluteus).* Such a result would be inconceivable did the egg possess a structure of such a degree of complexity as the adult animal. Zur Strassen \ had already before Driesch's experiments made the observation that the eggs of a parasitic FIG. 38. worm, Ascaris, occasionally give rise to giant embryos through the fact that two eggs fuse and that their combined masses now give rise to but one organism. If the egg possessed a complicated structure, the fusion of the masses of two eggs could no more give rise to a single individual of gigantic dimensions than two individual adult animals could be transformed into one by fusing their masses. I have also observed that with the proper chemical treatment the eggs of the starfish and of Ch&topterus can be caused to fuse; that from two or more such eggs a single giant embryo may result.^ Boveri and Driesch assume the existence of a certain simple struc- ture in the unfertilized egg of the sea urchin. According to Boveri, the egg protoplasm consists of three layers occupying different part 5 of the egg (see Fig. 6, p. 31). These three masses can still be recog- nized in the first four cleavage cells, but in the eight-cell stage cells arise
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