CHAPTER FOUR 
PHENOMENA WHICH REFUTE SIMPLE EPIGENESIS; AND 
PHENOMENA WHICH REFUTE PREFORMATION. INAD- 
MISSABILITY OF A HOMOGENEOUS GERM SUBSTANCE; 
AND INADMISSABILITY OF PREFORMISTIC GERMS. 
rt. Phenomena Which Refute Simple Epigenesis 
Roux designates, with the expression “self-differenti- 
ation” of a certain part of the organism, the process in 
which, according to a certain hypothesis, “the cause of 
whatever is specific in the differentiation of that part lies 
within this latter.” And he calls “dependent or correla- 
tive differentiation” the opposite process, in which, ac- 
cording to other hypotheses, whatever is specific in the 
alteration which goes on in a certain part of the organism 
during development is determined by causes lying outside 
this part.°° 
If an ontogeny consisted only of self-differentiations, 
we should designate the development as evolutionary. If 
on the contrary, an ontogeny were produced only through 
dependent differentiations, we should call that a process 
of epigenetic nature. 
Wilhelm Roux: Die Methoden zur Hervorbringung halber 
Froschembryonen und zum Nachweis der Beziehung der ersten 
Furchungsebene des Froscheies zur Medianebene des Embryo. Anat. 
Anzeiger, Bd. IX. February 1894, P. 277—278. Gesamm. Abhandl,, 
II, P. 978. 
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