THE WONDERS OP LIFE 



observers discovered in cell-division led to the theory 

 that the colorable part of the nucleus, chromatin, is 

 the real hereditary matter, or the material substratum 

 of the energy of heredity. Weismann added the theory 

 that this germ-plasm lives quite separately from the 

 other substances in the cell, and that the latter (the 

 soma-plasm) cannot transmit to the germ-plasm the 

 characters it has acquired by adaptation. It is on the 

 strength of this theory that he opposes progressive 

 heredity. The representatives of the latter (including 

 myself) do not accept this absolute separation of germ- 

 plasm from body-plasm; we believe that even in the 

 process of cell-division in the unicellular organism there 

 is partial blending of the two kinds of plasm (caryolysis), 

 and that in the multicellular organism of the histona 

 also the harmonious connection of all the cells by their 

 plasma-fibres makes it possible enough for all the cells 

 in the body to act on the germ-plasm of the germ-cells. 

 Max Kassowitz has shown how we can explain this 

 influence by the molecular structure of the plasm. 



At the beginning of the twentieth century a new bio- 

 logical theory aroused a good deal of interest, and was 

 welcomed by some as an experimental refutation of 

 Darwin's theory of selection and by others as a valuable 

 supplement to it. The distinguished botanist Hugo de 

 Bries (of Amsterdam) gave an interesting lecture at the 

 scientific congress at Hamburg in 1901 on "The Muta- 

 tions and Mutation-periods in the Origin of Species." 

 Supported by many years of experiments in selection 

 and some ingenious speculations, he thinks he has dis- 

 covered a new method of the transformation of species, 

 an abrupt modification of the specific form at a bound, 

 and so discredited Darwin's theory of their gradual 

 change through long periods of time. In a large work 

 on Experiments and Observations on the Origin of Species 

 in the Plant Kingdom (1903), De Bries has endeavored to 



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