240 Theories Treating of Inheritance 
in which it had arisen, and to suppose instead that when 
once the idioplasm has been modified there remains in it 
nothing more of the preceding states, not even in a latent 
or potential condition. At least this would seem to be 
indicated in the following passages. 
“The theory of biogenesis makes it necessary for us 
to introduce into Haeckel’s statement of the fundamental 
biogenetic law, a few modifications and explanatory addi- 
tions through which the contradiction (between this law 
and this theory) may be avoided. We should drop the 
expression: repetition of the forms of extinct ancestors, 
and substitute for it: repetition of forms which obey the 
laws of organic development and which progress from 
the simple to the complex. We should lay the emphasis 
upon this, that in embryonic forms, just as in the adult 
forms of animals, are expressed general laws of develop- 
ment of organized living substance.” 
“The periodically repeated development of pluricellu- 
lar individuals from unicellular representatives of the 
species, or individual ontogeny, is brought about in general 
accordance with the same rules as the preceding onto- 
genies, but becomes each time a little modified correspond- 
ing to the extent to which the characteristic cell of the 
species was modified in phylogeny.” 
“That certain conditions of form recur in the develop- 
ment of animals with such great constancy, and in the 
main in similar ways, is due chiefly to the fact that in all 
circumstances they furnish the prerequisite conditions 
under which the next later stages of ontogeny can be 
produced.” 
“The unicellular organism, on account of its very 
nature, can be transformed into a pluricellular organism 
‘ 
