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 



