THEORIES OF PANGENESIS 399 



§ 3. Theories of Pangenesis 



Passing from theological, metaphysical, and mystical inter- 

 pretations, we come to a whole series of theories, which are in 

 varying degrees scientific, and may be fairly enough described 

 by the general designation pangenetic. They all have this in 

 common, that they seek to explain the uniqueness of the germ- 

 cell by regarding it as a centre of contributions from different 

 parts of the organism. 



Early Forms. — We need not delay over the earlier and vaguer 

 forms of this supposition. At such different epochs as are sug- 

 gested by the names of Democritus and Hippocrates, Paracelsus 

 and Maupertuis, incipient theories of pangenesis — prophecies of 

 Darwin's — were suggested. Thus, Democritus maintained that 

 the " seed " of animals was elaborated by contributions from 

 all parts of the body, and that the constituent parts reproduced 

 in development the organs and parts from which they had 

 originated. Two millennia later, Buffon, of whose speculation 

 Darwin appears at first to have been unaware, again conceived 

 of the germs as mingled extracts from all parts of the body, or 

 as collections of samples from the various organs. If such were 

 indeed the case, Buffon and his predecessors saw no further 

 difficulty, for each contributed sample produced in the 

 development of the embryo a structure like its parental origin. 

 Bonnet (1776) was another who suggested the possibility of 

 molecules passing from the organs of the body to build up 

 the germ. 



Spencer's Theory of Physiological Units. — In 1861, the 

 physiologist Brucke emphasised the usefulness of assuming the 

 existence of biological units (Elemen(arorganismen) ranking 

 between the molecule and the cell. In July, 1863, Herbert 

 Spencer adopted a somewhat similar hypothesis of " physiological 

 units," lower in degree than the visible cell-units, but more 

 complex than the chemical molecules. As there is much in his 



