Download e-book for iPad: A Theory of the Formation of Animals by W. T. Hillier

By W. T. Hillier

ISBN-10: 1483200345

ISBN-13: 9781483200347

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Masses of plasticine were weighed out proportional to the number of cells formed from each quartette of micromeres, a different colour being used for each quartette. There were thus six masses of plasticine, one for each quartette and one for the residual macromeres. These masses were then moulded in as even a thickness as possible in the form of an upper and lower circular cap and four intermediate zones over the surface of an india-rubber R ball, so as to cover it in entirely. This of course was done on the assumption A c t h a t the ideal form of the embryo at this stage is a sphere, and t h a t the ideal D arrangement of the quartettes of micromeres is in successive belts.

I t seems obvious t h a t it is not at the half-way point of the length of the main axes t h a t this plane is situated, for if it were there, then there would be no reason for the flattening out. This phenomenon shows t h a t there is some distortion of the original dimensions, while the re-attainment of the globular shape at a later time shows t h a t the distortion is only temporary. , t h a t the inhibition of cell division of the cells of the fourth quartette is due t o this being the particular region where the four main axes are most firmly tethered together, so t h a t other activities are hindered, b u t as compensation for this, the necessarily more intimate union of the four components of the animal a t this locality results, later on, in an enhanced outburst of active growth.

Each contorted gutter consists of an enormous number of successive positions of the active meridian, and might have been drawn as shown in Fig. 23, if such a method of depicting t h e m would not have spoilt t h e clearness of 52 THE FORMATION OF ANIMALS the diagram as a whole. The curvature is probably to some extent variable adaptation t o circumstances; b u t such not be shown in the diagram, because of the meridians and capable of variations could it is not certain Fig. —Diagrams showing part of the paths of the active meridians of the phantom blastulse.

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A Theory of the Formation of Animals by W. T. Hillier

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