Pollen Mother-cells of Certain Plants. 43 
the same number of chromosomes issues from a nuclear reticulum as enters it, 
which conclusions have also been supported by Herla (’95), Morgan (’95), 
and Zoja (’95), in their studies on Ascaris. 
One of the principal objections raised against the hypothesis of 
chromosome individuality is the usual apparent loss to view of each 
chromosome, as Mottier (’03) claims for Podophyllum and L ilium , in the 
resting nuclei of many plants and animals. Even in such cases this 
objection is not entirely well founded, as Haecker (’04) and Gregoire (’07) 
have pointed out that the chromosomes are present as such in a more 
distributed form. They point out that during the telophases of division 
each chromosome by itself becomes transformed into a reticulum, so that 
the reticulum of a nucleus may be conceived of as being made up of a 
definite number of unit reticula. 
Although Haecker (’04) admits the truth of the hypothesis of 
chromosome continuity, he holds that in most cases only portions of the 
old chromosomes (‘Idomeren’ or ‘ Kernbezirke ’) are present in the 
differentiation of the new ones. He believes that the disappearance of 
the stainable material can be harmonized with the doctrine of continuity 
by regarding the achromatic portion or linin, and not the chromatin, as the 
continuous substance. This hypothesis is at least superfluous in such cases 
as Thalictrum , Calycanthus , and Richardia , in which the stainable material 
does not entirely disappear during rest. 
The Double Nature of the Somatic Nucleus. 
The acceptance of the doctrine that the chromosomes are permanent 
and that the parental elements remain separate throughout the life cycle of 
the organism, involves the conception that every nucleus derived from the 
nucleus of the fertilized egg is double, as first pointed out by Haecker (’92), 
containing two separate sets of chromosomes. It is of especial interest to 
determine, as far as possible, the fate of the parental chromatins in the 
offspring, and questions at once arise concerning the arrangement and 
grouping of the parental chromosomes in both somatic and germ nuclei, 
and also concerning the qualities of these elements. Acceptance of the 
doctrine of chromosome individuality also means that, at some period in 
the life cycle, these parental elements must be segregated, sorted out, or 
newly arranged, preparatory to being distributed to the gametes, and thus 
handed on from one generation to another. The facts thus established as 
to the behaviour of the chromosomes and their constancy in number in the 
sporophyte generation, show that each cell of the offspring, which develops 
from a normally fertilized egg, will contain elements one-half of which are 
purely paternal and one-half purely maternal in origin, and suggests the 
theoretical conclusion that the offspring will inherit equally from both 
