The cell in development and inheritance . 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 forma
The cell in development and inheritance . 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. Fig. 145. — Evidence of the individuality of the chromosomes in the egg of Ascaris. [BOVERI.] E. Anaphase of the first cleavage. F. Two-cell stage with lobed nuclei, the lobes formed bythe ends of the chromosomes. G. Early prophase of the ensuing division; chromosomes re-form-ing, centrosomes dividing. H. Later prophase, the chromosomes lying with their ends in thesame position as before; centrosomes divided. maintained. As the long chromosomes diverge, their free ends arealways turned toward the middle plane (Fig. 31), and upon the re-construction of the daughter-nuclei these ends give rise to correspond-ing lobes of the nucleus, as in Fig. 145, which persist throughout theresting state. At the succeeding division the chromosomes reappearexactly in the same position, t/icir ends lying- in the nuclear lobes asbefore (Fig. 145, G, H). On the strength of these facts Boveri con-cluded that the chromosomes must be regarded as * individuals or elementary organisms, that have an independe
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectcells, bookyear1902
