vision. (In 1887 W. Flemming termed this the
heterotypic form of nuclear division.) This stage in division determines
the conditions for the second division which rapidly ensues. Each of the
paired chromosomes of the mother-nucleus has already, as in an ordinary
nuclear division, completed the longitudinal fission, but in this case
it is not succeeded by the immediate separation of the longitudinal
halves and their allotment to different nuclei. Each chromosome,
therefore, takes its two longitudinal halves into the same
daughter-nucleus. Thus, in each daughter-nucleus the longitudinal halves
of the chromosomes are present ready for the next stage in the
division; they only require to be arranged in the nuclear plate and then
distributed among the granddaughter-nuclei. This method of division,
which takes place with chromosomes already split, and which have only
to provide for the distribution of their longitudinal halves to the next
nuclear generation, has been called homotypic nuclear division. (The
name was proposed by W. Flemming in 1887; the nature of this type of
division was, however, not explained until later.)

Reduction division and homotypic nuclear division are included together
under the term allotypic nuclear division and are distinguished from the
ordinary or typical nuclear division. The name Meiosis (By J. Bretland
Farmer and J.E.S. Moore in 1905.) has also been proposed for these two
allotypic nuclear divisions. The typical divisions are often spoken of
as somatic.

Observers who were actively engaged in this branch of recent
histological research soon noticed that the chromosomes of a given
organism are differentiated in definite numbers from the nuclear
network in the course of division. This is especially striking in the
gonotokonts, but it applies also to the somatic tissues. In the latter,
one usually finds twice as many chromosomes as in the gonotokonts. Thus
the conclusion was gradually reached that the doubling of chromosomes,
which necessarily accompanies fertilisation, is maintained in the
product of fertilisation, to be again reduced to one half in the
gonotokonts at the stage of reduction-division. This enabled us to form
a conception as to the essence of true alternation of generations, in
which generations containing single and double chromosomes alternate
with one another.

The single-chromosome generation, which I will call the HAPLOID, must
have been the primitive generation in all o