INHERITANCE 
9 
a way that half the chromosomes are in one group and the 
other half in another group. One of these groups is expelled 
from the cell and plays no further part in the inheritance 
game. The other group remains in the cell as a half nucleus. 
In some unexplained way, the qualities which offspring in¬ 
herit from parents are conveyed through the chromosomes. 
Certain qualities are tied up with one color body and other 
qualities with other color bodies. Since 
the mother’s inheritable qualities go with 
the chromosomes, one half of them are 
discarded with the expelled group of color 
bodies and the other half are transmitted 
to the offspring through the retained color 
bodies. Which chromosomes are dis¬ 
carded in any case and which are retained 
seems to be a matter of chance and can 
not be foretold. 
The sperm cell, when preparing to fer¬ 
tilize the egg cell, also divides into two 
spermatozoa in such a way that each con¬ 
tains only half the number of chromo¬ 
somes. One of these spermatozoa unites 
with the half nucleus of the egg cell, thus 
joining half the transmissible qualities of 
the father with half those of the mother 
and producing a nucleus with the full 
number of chromosomes. As the fertil¬ 
ized egg cell grows, it divides in such a way as to split each 
color body, thus retaining the full number of chromosomes 
in each cell of the young which develops from the egg. 
1. How does the maturation division of the nucleus differ from 
the growth division? Compare Figure 8 with Figure 9. 
2. What becomes of each half of the nucleus? Figure 9. 
3. Why does the offspring inherit only half of the mother’s trans¬ 
missible qualities? 
Figure 10. — A Sperm 
Cell Dividing into 
Two Spermatozoa. 
Each spermatozoon 
carries one half the 
number of color bodies 
of the original sperm 
cell. 
