Form Not Dependent on Number of Divisions 131 
is produced, the heart of the complete tadpole putting 
in circulation the blood of the grafted portion also,!% 
This phenomenon is presented also very strikingly 
in the mutual prolongation one into another of the 
pronephric and other secretory ducts. Thus in a double 
monster obtained by uniting the anterior portions of two 
tadpoles, the left pronephric ducts met and grew together 
although at first their extremely fine cut ends certainly lay 
some distance apart and their directions crossed almost at 
right angles.104 
All these phenomena are hard to reconcile with the 
rigidity implied in Weismann’s determinants. They 
speak on the contrary entirely in favor of a general 
process of growth that is epigenetic in nature; for only 
to a process of growth of this nature can be ascribed 
all the phenomena of adaptation and of deviation from 
the normal form which result in the complete and exact 
conjunction of the various corresponding portions of 
different individuals. 
Against the rigid preformation of Weismann, which 
attributes development exclusively to qualitative nuclear 
divisions, Roux himself furnishes a most appropriate 
argument which even the most pronounced anti-preform- 
ists rarely cite. 
“In the larger animals of the same species the cells 
are not correspondingly larger than in individuals 
which in consequence of lack of nourishment have re- 
mained smaller. Thus the unequal size of the individuals 
must be associated with an unequal number of cell 
divisions, which by the method of qualitative differentia- 
tion assumed by Weismann must lead to a very essential 
1°°G. Born: Ibid. P. 87—88. 
101G, Born: Ibid. P. 144. 
