. The wonder of life. Biology; Natural history; Zoology. THE CYCLE OF LIFE 387 unfertilized egg; the cells of the body had only half the normal number of chromosomes. In some cases the number seems to be normal, which may be due to the fact that the ova began to develop under arti- ficial stimulus before the ordinary reduction process had occurred; or to a subsequent restoration of the reduced number ' by a process of auto-regulation', as is said to be the case in Delage's parthenogenetic sea- urchin larvae. The general opinion of experts is thus summed up by Professor E. B. Wilson. As the ovu
. The wonder of life. Biology; Natural history; Zoology. THE CYCLE OF LIFE 387 unfertilized egg; the cells of the body had only half the normal number of chromosomes. In some cases the number seems to be normal, which may be due to the fact that the ova began to develop under arti- ficial stimulus before the ordinary reduction process had occurred; or to a subsequent restoration of the reduced number ' by a process of auto-regulation', as is said to be the case in Delage's parthenogenetic sea- urchin larvae. The general opinion of experts is thus summed up by Professor E. B. Wilson. As the ovum is much the larger, it is beheved to furnish the initial capital —including in some cases a legacy of food-yolk—for the early development of the embryo. From both parents ahke comes the inherited organization which has its seat (in part at least) in the readily stainable chromatin rods or chromo- somes of the nucleus. From the father comes a httle body, the centrosome, which organizes the machinery of division by which the egg spUts up, and distributes the dual inheritance equally between the daughter-cells. Besides bearing the paternal inheritance, restoring the number of chromosomes to the normal, introducing the centrosome (which serves as 'the weaver of the loom'), and acting as the normal trigger-puUer which sets the egg a-going on the path-. FiG. 61.—^Diagramof a cell, l,the nucleus ; 2, the chromosomes, or readily stainable bodies in the nucleus ; 3, the cell sub- stance or cytoplasm showing a, reticular structure ; 4, the 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 perfectly resemble the original Thompson, John Arthur, Sir, 1861-1933. London, A. Melrose, Ltd
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