18 Biogenetic Law of Recapitulation 
development nor indeed have any part whatever in it; 
that would fall entirely to the other portion alone, and it 
would be just this passivity which would secure the in- 
alterability of the germ plasm: 
While on the other hand the epigenesists consider that 
the idioplasm would participate in an important and con- 
tinuous way in development, because it would be present 
and active at every instant and in all cells; it would 
remain, however, in spite of this participation permanently 
unaltered, so that the cells of the soma would never be- 
come differentiated by nuclear somatization from the 
germ cells, but on the contrary retain the capacity of 
reproduction to the same extent: 
The centroepigenetic hypothesis postulates on the con- 
trary that the germinal substance, although limited to a 
single zone and separated and differentiated from the rest 
of the soma, nevertheless exercises its epigenetic, forma- 
tive action upon all the rest of the organism and during 
the whole of development, without undergoing any altera- 
tion whatever through this participation in development. 
But this hypothesis thus sketched must now be made 
more precise and clear by the consideration of other series 
of phenomena, while at the same time the proof of the 
facts is undertaken. And to this we propose to proceed 
in the chapters which follow. 
