SOMATOPLASM AND GERM-PLASM 533 
that does not have to do directly with forming sex cells is called 
somatoplasm. Thus the protoplasm of all vegetative structures 
of plants, such as leaves, roots, and stems, is somatoplasm. 
Even the parts of a flower, excepting the protoplasm immedi- 
ately involved in the production of sex cells, is somatoplasm. 
According to Weismannism, the characters of a species are de- 
termined by certain units or factors within the germ-plasm 
and the germ-plasm remains practically the same from genera- 
tion to generation in respect to the factors contained, although 
the factors may change in reference to each other. He holds 
that changes in the somatoplasm, such as those variations in 
leaves, roots, and stems that occur in response to environmental 
influences, are not imparted to the germ-plasm and consequently 
are not inheritable. This theory that the germ-plasm remains 
practically the same throughout generations is known as the con- 
tinuity of the germ-plasm. Since modifications in the somato- 
plasm leave no trace of themselves in the germ-plasm, it is obvi- 
ous that, according to Weismann’s view, characters cannot be 
acquired. This means that any trait which an individual does 
not inherit but acquires during its life time in response to envi- 
ronment is not transmitted to the offspring. Thus, if a parent 
acquires great skill as a musician, mathematician, or in other 
lines, the children of this parent inherit none of this acquired 
ability. Also, in case of plants, the particular modifications 
which individuals take on during their life time disappear with 
the individuals. 
In accounting for the inheritable changes occurring in indi- 
viduals and generations, Weismann tells us that the units or 
factors in the germ-plasm are changing in relation to each 
other, and these changes account for the origin of new char- 
acters. Some units may become stronger and others weaker, 
and they may combine in various ways. Such changes may be 
induced by external conditions, such as poor nourishment, 
drought, competition, etc., but the character resulting there- 
from may be of any kind, and hence only by chance is it of such 
a nature as to adjust the individual to its environment. For 
example, the changes induced in the units of germ-plasm by an 
environmental factor, such as drought, may result in a change 
in the color of the flower, length of style, arrangement of leaves, 
etc. Thus the character resulting from the change induced by 
