Heredity and its Bearings on Atavism. 139 
Ascaris ; while in some cases they may number a hundred 
or even more. If now an organism possess, say, several 
chromatin segments, and if it undergo evolution, it is con- 
ceivable that the metabolism may become evolved along such 
divergent lines that the proper performance of al the 
functions by each single segment becomes difficult if not 
impossible. Further, as the various segments in a nucleus 
are not under conditions identically the same, I infer that 
each segment will evolve along such lines as are facilitated 
by its relative position in the organism. 
Thus we would be dealing with the following factors :— 
1. A unicellular organism possessing several nuclear seg- 
ments, each of which fulfils functions somewhat 
different from those performed by the other segments. 
2. A division of functions between the various segments, 
allowing progressive or evolutionary changes to take 
place more readily in each segment. 
3. The sum total of metabolism raised in the nuclear 
segments. 
4, Corresponding evolutionary changes in all the other cell 
organs. 
5. The cell-metabolism rendered more and more complicated. 
Given such a cell with a very complicated organisation, 
and with its various plasmata consisting of comparatively 
unstable compounds ready to undergo further evolution, we 
can understand how a division into two equally organised 
daughter-cells will become gradually more and more difficult, 
and ultimately impossible. The unicellular organism must 
therefore give rise to two daughter-cells which differ in some 
respects from one another, and the fate of the latter I can 
perhaps best explain with the aid of Verworn’s figure 
(p. 151). 
If a cell « divide into two cells A and B, of which 
the cell A is especially abundant in “ nuclear” matter, while 
the cell B is rich in cell-plasm, it is evident that both cells 
will metabolise materials, essential to the life of each cell, 
but in varying quantities. The cell A, rich in “nuclear” 
matter, will especially elaborate the substances s and h, 
