Centroepigenesis Accords with General Phenomena 69 
normal circumstances which have made them independent 
of each other, two distinct nodal points,—two central 
zones of development. The necessary consequences of 
the independent action of these two centers of develop- 
ment would be the centration of each individual by itself. 
On the other hand, the similarity of the two first blasto- 
meric nuclei, which through multiplication give rise to 
both of the two central zones concerned, would bring 
about a similarity of the formative actions given off from 
these zones. Therefore those formative stimuli which 
act upon all points of any one of the infinite number of 
planes symmetrical in relation to these centers, would 
offset and annul one another, because they would be 
equal and opposite but only in so far as they do act 
along these planes. In this way could be explained why 
the parts lacking in both individuals must always be alike. 
While thus all these different facts which have at- 
tracted the careful attention of Roux and been made the 
special object of his studies confirm, some directly others 
indirectly, the hypothesis of centroepigenesis with ram- 
ifying and independent networks of correlation, a further 
support, indirect indeed, but nevertheless very real, will 
be brought forward in the following chapter. For we 
shall endeavor there to show that if a whole series of 
facts compels us to throw over preformation, a series of 
other facts forces us to throw over simple epigenesis also, 
and this would give a high degree of probability to. any 
other hypothesis with which both series of facts should 
be in accord. 
Finally, the symmetrical disposition which the greater 
number of organisms present in relation to a point, to a 
straight line, or to a plane, and also the advance of 
growth along diverging ramifications, which indeed is a 
