232 
HAROLD’S DISCUSSIONS. 
Within certain limits variation is produced hy hered¬ 
ity itself. 
Living organisms reproduce in various ways—by 
division, by budding, by spores, and by conjugation. 
The first three are usually asexual. The more highly 
organized plants and animals reproduce by the union 
of germ-cells, male and female. In the reproduction 
of unicellular organisms there is but little chance 
for variation. The unicellular germ-cell embodies in 
itself a single line of hereditary infiuences, but in the 
higher organisms we have the union of two lines at 
least of hereditary infiuences, and the less closely 
they are related to each other the more diverse will 
be their characteristics. 
The child often resembles the mother in some re¬ 
spects and the father in others; sometimes the char¬ 
acteristics are so combined that it is difficult to say 
which of the parents the child resembles. The eyes, 
the ears, the shape of the head, the nose, the chin, the 
form of the body and the carriage, the mental char¬ 
acteristics—all are subject to these laws. Sometimes 
the child resembles the grandparents or possibly still 
earlier ancestors. This tendency to go back is atavism. 
It seems, then, that hereditary infiuences are treas¬ 
ured up from generation to generation, each mar¬ 
riage adding new characteristics to the life stream. 
We often hear it said that a certain person is “ a chip 
from the old block,” but it would be nearer the truth 
to say that he is ‘‘ a chip from many old blocks.” 
It can not be denied that environment and natural 
selection are most potent in producing modifications 
