28 HEREDITY AND SELECTION IN SOCIOLOGY 



development or ontogenesis, and for ontogenesis alone. Each 

 cell of the body contains germ-plasm in an active condition ; but 

 this active germ-plasm, though enabling the body-cell to repro- 

 duce itsdf, is not present in sufficient strength to enable the 

 somatic cell to reproduce the whole body. Active germ-plasm, 

 adapted to the needs of the individual development, and located 

 in the soma, dies with the soma. Inactive germ-plasm, on the 

 contrary, adapted to the maintenance of the race, and located 

 solely in the cells of the reproductive organs, is transmitted from 

 one generation to another, and guarantees the stability of the 

 racial history or phylogeny. 



Thus every organism may be said to be born with a store of 

 germ-plasm in two forms. The active germ-plasm of the embryo 

 presides, metaphorically speaking, over the building up of the 

 body-frame ; it passes into every cell of the body, bequeathing^ 

 to each its capacity of organisation and development. The 

 inactive germ-plasm is a reserve substance, subjected solely to 

 the quantitative changes of growth. It remains in the germ- 

 cells, is adapted to the reproduction of the species, and it is 

 necessarily endowed with potential immortality. 



We have seen that the hereditary substance of germ-plasm is 

 located in the cell nucleus, and we have seen that the extra- 

 ordinary precision of the movements of the chromosomes during 

 karyokinesis and during the process of maturation, justifies our 

 conclusion that the germ-plasm is located in the chromosomes. 

 The chromosomes, or ids, constitute the entire germ-plasm of the 

 nucleus. These ids do not form a homogeneous substance. On 

 the contrary, it is supposed that each id is formed by a number 

 of autonomous living units— the determinants, so called because 

 each determinant, or each group of determinants, determines the 

 structure, organisation, and composition of a corresponding cell 

 or group of cells in the fully formed organism. But the deter- 

 minants are not the ultimate vital units. The determinants 

 themselves must have a complex nature, and are supposed to 



