CHAPTER Vin 



Darwin, Naegeli, DeVries, and their 

 Theories of Heredity 



Theories based upon representative particles. — Darwin's pan- 

 genesis; gemmules representing the cells of the body; their 

 migration through the organism. — Objections. — Particles 

 representing properties of the organism. — Naegeli's theory; 

 the micellae and their groupings; the two types of proto- 

 plasm; elementary characters. — Discussion of this system. — 

 De Vries' theory; the pangenes, their migration through the 

 cells. 



DARWIN'S theory was formulated in 1868, soon 

 after Spencer's. It followed closely upon the 

 scientific discoveries as to the cellular constitution of 

 tissues. 



According to Darwin, the various cells of the or- 

 ganism derive their properties from tiny particles 

 which he designates as gemmules. These particles, of 

 which there are as many varieties as there aie cate- 

 gories of cells in the organism, are infinitely small, 

 can move through the membranes and multiply by 

 cleavage. The gemmules enter the various cells dur- 

 ing the cells' embryonic development; they multiply 

 within the cells until the cells have become definitively 



119 



