412 



BREAKDOWN OF GENETIC SYSTEMS 



mere. This anomalous behaviour is presumably a means of 

 structural change (cf. Nishiyama, 1931). 



The daughter univalents usually lag at the second division or 



Fig. 127. — The various possible courses that meiosis may follow 

 when several univalents or multivalents are formed, leading 

 to (i) irregular reduction, (ii) non-reduction at either first or 

 second division, (iii) double non-reduction. 



pass without division to one pole or the other. With division at 

 either the first or the second division, univalents are lost in the 

 cytoplasm through failure to reach the poles. 



Where all, or nearly all, the chromosomes are univalent their 

 relationship to the spindle is often abnormal. Sometimes the 



