138 Facts Compelling Us to Reject Pre formation 



trolling determinants also all the determinants of the 

 forearm and of the hand as accessory idioplasm, for they 

 can cause the entire chain of these bones to be formed 

 anew; and the cells of the radius must contain as acces- 

 sory idioplasm all the determinants of the radial portion 

 of the wrist, hand and fingers. 



"We can regard this theoretical requirement as quite 

 realizable also, since when the whole organ commences 

 to be formed, the necessary accessory idioplasm can very 

 well separate from the disintegrating embryonic idio- 

 plasm. We need only assume that this accessory idio- 

 plasm remains henceforth inactive in the nuclear sub- 

 stance of the cell until some cause for regeneration 

 arises." 111 



We note at once that, according to this hypothesis, 

 there is no reason at all why there should be held in re- 

 serve in each part of the bone only the accessory idio- 

 plasm capable of regenerating the bony parts distal to 

 that point, but never any other capable of regenerating a 

 larger or smaller part. Each particular reserve idioplasm, 

 when once it has separated itself in a given cell from the 

 principal idioplasm, and been segregated in the nucleus of 

 the cell itself in the latent state, will be able to preserve 

 itself unaltered through many generations of cells. Con- 

 sequently there must be present at any point at which a 

 bone may be broken several accessory idioplasms, each 

 capable of regenerating a more or less long portion of the 

 bone which was broken, and perhaps also of some other 

 bone. In the illustrative case cited by Weismann the sec- 

 ond phalanx should contain besides the reserve idioplasm 

 capable of regenerating the second and third phalanx, 



111 Weismann : Das Keimplasma. P. 136138. 



