INVESTIGATIONS SINCE MENDEL 555 
of the plant or animal whose cell is dividing organizes separately 
into chromosomes, thus one-half of the number of chromosomes 
being composed of father chromatin and the other half being com- 
posed of mother chromatin. This means that the chromosomes 
contributed to the offspring by each of the parents maintain 
their individuality in the offspring. In vegetative cell division 
each chromosome splits longitudinally, and to each new nucleus 
there is contributed a half of each chromosome. It is obvious 
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Fic. 482. — A diagram illustrating the behavior of chromatin in the reduc- 
tion division. For convenience the chromatin contributed by the father of 
the plant, the division of whose cell the diagram illustrates, is shown black 
and the chromatin contributed by the mother plant is shown white. In the 
upper line, organization of the chromosomes and their pairing, each pair con- 
sisting of one father and one mother chromosome; in the lower line, the dis- 
tribution of the chromosomes in the formation of the daughter nuclei. In 
this case one of the daughter nuclei reccives one father and three mother 
chromosomes, while the other daughter nucleus receives one mother and three 
father chromosomes, but this is only one of a number of ways of distributing 
the chromosomes. 
that the vegetative cell division tends to distribute the chromatin 
from both parents equally to the new nuclei. But in the reduc- 
tion division, as shown in Figure 482, whole chromosomes and 
not halves are contributed to each new nucleus, and conse- 
quently the new nuclei resulting from the reduction division 
receive only half as many chromosomes as the mother cell con- 
tained. In the reduction division the chromosomes contributed 
to the daughter nuclei may be only those of the mother parent or 
only those of the father parent, in which case the daughter nuclei 
