II.] weismann's hypothesis. 61 



and of their concentration in the sexual system; yet 

 it should be said that a simpler one which can account 

 for the facts has not yet been advanced, unless it be 

 the bathmic hypothesis of Cope (or similar formula- 

 tions of the conception of the growth -force), which 

 supposes that each body -cell transmits "a mode of 

 motion" to the germ -cell. 



For the present purpose, we need consider but one 

 other hypothesis of heredity — that advanced in 1883 by 

 VVeismann, which has given rise to the philosophy now 

 called Neo- Darwinism. Weismann's point of view is 

 interesting and unique. He places himself at the thresh- 

 old of organic life, and contemplates what takes place 

 in the reproduction of one-celled organisms. These or- 

 ganisms multiply largely by simple division, or fission. 

 When the organism reaches a certain size, it becomes 

 constricted near its middle, and finally parts into two 

 cells or organisms. It is evident that one organism is 

 twin of the other, neither is older, neither is parent, but 

 each has partaken of the common stock of protoplasm. 

 The protoplasm again multiplies itself in the two organ- 

 isms, and at length it is again divided; and so, to the 

 end of time, the remotest individual of the series may be 

 said to contain a portion of the original protoplasm; in 

 other words, the protoplasm is continuous. And inas- 

 much as protoplasm is the seat or physical basis of life, 

 it may be said that the one -celled organism is immortal, 

 or is not confronted by natural death. 



In time, however, there came a division of labor — 

 cells living together in colonies, and certain cells per- 

 forming one function and certain other cells other func- 

 tions. This was, perhaps, the beginning of the many- 

 celled organism, in which certain cells developed the 



