336 MUTATIONS 



entiation begins, one cell or more will be set aside to produce future 

 germ cells. . The other cells go on multiplying and form the soma, 



father' 



According to August Weismann germ plasm is derived from the germ plasm of previous 

 generations. Thus it is continuous from one generation to another. Successive generations 

 must resemble each other since they are all derived from the same germ plasm. Somatoplasm 

 develops from germ plasm. 



or body cells. From the former cells, there develop all the germ 

 cells of the organism. Germ cells consist of germ plasm, body cells 

 of somatoplasm. When some of the germ cells of one individual 

 meet the germ cells of another individual, they will unite, and, 

 while still in the form of germ plasm, a small portion of it will be set 

 aside to form the germ cells of the embryo. Thus the germ plasm 

 is continuous from one generation to the next. 



This continuity of germ plasm has actually been demonstrated. 

 One observer records that when, in a certain worm, the sixteenth 

 cell stage of the embryo is reached, one cell is set aside to form the 

 germ plasm and the other fifteen of the cells form somatoplasm. 



Mutations. It has already been stated that variations of the 

 body plasm, which occur during the life of the individual, such as 

 dwarfing of trees by wind and the acquiring of muscular skill, are 

 generally considered not inheritable. These are often called 

 acquired characters. Acquired characters are somatic variations 

 which are due to environment and are not as a rule transmitted 

 from parent to offspring. Some experimentation has recently been 

 undertaken to show that, under certain conditions, acquired char- 

 acters may be transmitted from parent to offspring. But, since 

 these abilities were acquired by the soma cells long after the germ 



