VARIATION 207 



environmental influences acting upon the soma-cells or 

 from variations directly affecting the germ-plasm itself. 



Many new characters appearing in plants and animals 

 cannot be traced to environmental influences acting upon 

 the soma-cells. Many characters seem to arise inde- 

 pendently of external causes. They undoubtedly have 

 their origin in the germ-plasm itself. Such variations 

 are fundamentally different from the characters which 

 are acquired by the soma-cells as the result of environment, 

 use or disuse, disease and mutilations. 



The germ-cell which contains within its own substance 

 the materials needed for giving direction to the develop- 

 ment of the new individual is the result of the union of 

 two other germ-cells from individuals which may repre- 

 sent widely different characters. It is impossible that 

 the new individual arising from such a germ-cell shall 

 possess characters identical with either parent. The 

 offspring represents a certain amount of variation which 

 had its origin in the germ-cell itself. 



The mechanism of reproduction, including the matura- 

 tion and reduction of the germ-cells and the union of the 

 chromosomes, provides ample opportunity for new com- 

 binations of characters which may profoundly change 

 the whole physiological history of the offspring. 



196. Mutilations. Many examples of mutilations 

 and their supposed transmission from parent to offspring 

 have given to advocates of the belief in the transmission 

 of acquired characters many of their most interesting 

 examples. Various investigators have cut off the tails 

 of mice for many generations with a view to investigating 

 the result of such mutilation upon its transmissibility. 

 Cope, Mantegazza and Rosenthal cut off the tails of mice 

 for eleven generations, Bos for fifteen, and Weismann 



