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. 100 



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. 101 



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 



100 G. Born : Ibid. P. 87-88. 

 101 G. Born: Ibid. P. 144. 



