Caroline Pbllew and Eva Richardson Sansome 49 



number of chiasmata, ten, is very high, being four more than that 

 observed in any other association. This may be a coincidence — or it may 

 be that the interlocking affects the number of chiasmata, either by 

 increasing the number of breaks at an early stage or more probably by 

 hindering terminahsation. 



In some cases (see Fig. 6) the association of chromosomes is orientated 

 so that adjacent chromosomes are directed towards the same pole. Such 

 an arrangement gives non-disjunction, only one segment in each chromo- 



4 



Fig. 10. Two early anaphases from a semi-sterile plant 696730. In (a) two adjacent 

 chromosomes from the ring are passing to each pole. In (6) three chromosomes from 

 the ring are passing to one pole and one to the other, x 4000. 



some disjoining from its homologue. Fig. 8 shows associations in which 

 the chromosomes are arranged in a zigzag, opposite chromosomes going 

 to the same pole. In these cases, each chromosome segment goes to the 

 opposite pole from its homologue, giving disjunction. Fig. 10 a shows 

 an early anaphase in which adjacent chromosomes from the ring can be 

 seen going to the same pole. 



Occasionally three chromosomes are directed towards one pole, and 

 anaphase figures have been observed in which eight chromosomes are 

 seen going to one pole and six to the other (see Fig. 10 b). If such 



