rganisms; it might also
persist as the only generation. Every sexual differentiation in
organisms, which occurred in the course of phylogenetic development, was
followed by fertilisation and therefore by the creation of a diploid or
double-chromosome product. So long as the germination of the product
of fertilisation, the zygote, began with a reducing process, a special
DIPLOID generation was not represented. This, however, appeared later
as a product of the further evolution of the zygote, and the reduction
division was correspondingly postponed. In animals, as in plants, the
diploid generation attained the higher development and gradually assumed
the dominant position. The haploid generation suffered a proportional
reduction, until it finally ceased to have an independent existence and
became restricted to the role of producing the sexual products within
the body of the diploid generation. Those who do not possess the
necessary special knowledge are unable to realise what remains of the
first haploid generation in a phanerogamic plant or in a vertebrate
animal. In Angiosperms this is actually represented only by the short
developmental stages which extend from the pollen mother-cells to the
sperm-nucleus of the pollen-tube, and from the embryo-sac mother-cell to
the egg and the endosperm tissue. The embryo-sac remains enclosed in
the diploid ovule, and within this from the fertilised egg is formed
the embryo which introduces the new diploid generation. On the full
development of the diploid embryo of the next generation, the diploid
ovule of the preceding diploid generation is separated from the latter
as a ripe seed. The uninitiated sees in the more highly organised plants
only a succession of diploid generations. Similarly all the higher
animals appear to us as independent organisms with diploid nuclei only.
The haploid generation is confined in them to the cells produced as the
result of the reduction division of the gonotokonts; the development of
these is completed with the homotypic stage of division which succeeds
the reduction division and produces the sexual products.

The constancy of the numbers in which the chromosomes separate
themselves from the nuclear network during division gave rise to the
conception that, in a certain degree, chromosomes possess individuality.
Indeed the most careful investigations (Particularly those of V.
Gregoire and his pupils.) have shown that the segments of the nuclear
networ