THK PHYSICAL BASIS OF HEREDITY. 27 



Their difference only an apparent one. Fundament- 

 ally alike, as seen in their development. 



V. Fertilization and Amphimixis. 



VI. Recent Theories of Heredity. Their use as work- 

 ing hypotheses. * Even error, if it originate in correct 

 deductions, must become a step towards truth." Dar- 

 win, Spencer, (lalton. Brooks, Niigeli. DeVries, Weis- 

 mann, Wiesner. 



VII. View* of Weixmann. Morphoplasm and idio- 

 plasm. The structure of the germ plasm. The 

 chromosomes or idants the bearers of heredity ten- 

 dencies. These made up of : 



1. Biophore*. or Lebenstrager, the ultimate vital 

 units. Various, but perfectly definite numbers of 

 them form 



'2. Determinant*, vital units of the second order. 

 Each of these is the Anlage of a particular cell or 

 group of cells. r J hese constitute &nd occupy definite 

 positions in the architecture of the vital units of the 

 third order, the 



8. Id*. In the process of development of the in- 

 dividual, its ontogeney, these ids break up with a 

 qualitative distribution of each group of determinants 

 to its appropriate place in the adult organism. These 

 ids may correspond to the visible " microsomes." 



4. The origin of variations. 



