432 



BREAKDOWN OF GENETIC SYSTEMS 



When the multiple chromosomes are broken in the middle, instead 

 of giving monocentric and acentric fragments, they yield two or 

 more functional chromosomes. 



The theoretical consequences of the breakage of chromosomes 



Fig. 129. — Metaphase, anaphase and telophase of the second cleavage 

 division and metaphase of the third in Ascaris showing frag- 

 mentation and diminution of the polycentric chromosomes. 

 (Boveri, 1904.) 



by irradiation are manifold. Its bearing on the theory of the 

 gene has already been discussed. Its bearing on the theory of 

 structural change, especially the question of whether delayed 

 reunion can take place, will be considered later. It is of immediate 

 importance, however, to the theory of the centromere and of its 



