THEORIES OF EVOLUTION 159 



acquired characters that is, of acquisition made by 

 the body-cells, or changes arising in them, during the 

 lifetime of the individual. None of the body-cells are 

 transmitted and the hereditary qualities must all be 

 located within the plasms of the germ-cells. 



The outstanding features of Weismann's theory 

 are as follows: 



1. The germ-plasm has unbroken continuity from 

 the beginning of life. 



2. Heredity is accounted for on the principle that 

 the offspring is composed of some of the same stuff 

 (germ-plasm) as its parents. The body-cells are not 

 inherited. 



3. Consequently, there is no inheritance of ac- 

 quired characters. 



4. Variations arise from the union of the germinal 

 elements, giving rise to varied combinations and 

 permutations of qualities of the uniting germ-plasms. 



5. Weismann adopts and extends the principle of 

 natural selection. 



De Vries. Hugo de Vries (Fig. 33), director of 

 the Botanical Garden in Amsterdam, has experi- 

 mented widely with plants, especially the evening 

 primrose (CEnothera Lamarckiana) , and has shown 

 that different species appear to rise suddenly. These 



