194 Pang ens in the Nucleus and Cytoplasm 



species. The visible phenomena of heredity are hence 

 the expressions of the characters of minutest invisible 

 particles, concealed in that living matter. And we must, 

 indeed, in order to be able to account for all the phenom- 

 ena, assume special particles for every hereditary char- 

 acter. I designate these units, pangens. 



These pangens, invisibly small, yet of quite another 

 order than the chemical molecules, and each of them com- 

 posed of innumerable such molecules, must grow and 

 multiply, and must be capable of distributing themselves 

 by means of ordinary cell-division, over all or at least 

 nearly all cells of the organism. They are either inac- 

 tive (latent), or active, but they can multiply in both 

 states. Predominantly inactive in the cells of the germ- 

 tracks, they usually develop their highest activity in the 

 somatic cells. And this in such a way, that, in higher 

 organisms, not all the pangens of any given cell probably 

 ever become active, but in every cell one or more of the 

 groups of pangens dominates and impresses its character 

 on the cell. 



Fertilization consists in a fusion of nuclei. The 

 offspring receives from the father only that which was 

 contained in the nucleus of the sperm. All the hereditary 

 characters must therefore be represented in the nuclei 

 by their respective pangens. Nuclei, therefore, are to 

 be regarded as the reservoirs of hereditary characters. 



In the nucleus, however, by far the most of the char- 

 acters remain latent all through life. They become active 

 only in the other organs of the protoplast. Haeckel has 

 already said "that the nucleus within had to take care of 

 the transmission of the hereditary characters, and the 

 surrounding plasm, of the adjustmment, accommodation, 

 or adaptation to environmental conditions." (Cf. p. 169). 



