The cell in development and inheritance . ult which de-monstrates that the number of chromo-somes is not due merely to the chemicalcomposition of the chromatin-substance,but to a morphological organization ofthe nucleus. A beautiful confirmationof this conclusion was afterward madeby Boveri (93, 95, i) and Morgan (95,4), in the case of echinoderms, by rear-ing larvae from enucleated egg-fragments, fertilized by a single sper-matozodn (p. 194). All the nuclei of such larvae contain but half thetypical number of chromosomes, — in Echimis nine instead ofeighteen, — since all are descended fr
The cell in development and inheritance . ult which de-monstrates that the number of chromo-somes is not due merely to the chemicalcomposition of the chromatin-substance,but to a morphological organization ofthe nucleus. A beautiful confirmationof this conclusion was afterward madeby Boveri (93, 95, i) and Morgan (95,4), in the case of echinoderms, by rear-ing larvae from enucleated egg-fragments, fertilized by a single sper-matozodn (p. 194). All the nuclei of such larvae contain but half thetypical number of chromosomes, — in Echimis nine instead ofeighteen, — since all are descended from one germ-nucleus insteadof two! Equally striking is the remarkable fact, described at page 275, thatall of the cells in the sexual generation (oophore) of the highercryptogams show half the number of chromosomes characteristic ofthe sporophyte, the explanation being that while reduction occursat the time of spore-formation, the spores develop without fertilization,the reduced chromosome-number persisting until fertilization occurs. Fig. 144. — Giant-embryo of Ascaris,var. bivalens, arising from a double-fertilized double egg, showing eightchromosomes {ZMr Sirassen). MORPHOLOGICAL COMPOSITION OF THE NUCLEUS 297 long afterward. Attention may be again called to the surprising caseof Artemia, described at page 281, which gives a strong argument infavour of the hypothesis. In addition to the foregoing evidence, Van Beneden and Boveriwere able to demonstrate in Ascaris that in the formation of thespireme the chromosomes reappear in the same position as thosewhich entered into the formation of the reticulum, precisely as Rabl
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectcells, bookyear1902
