66 THE CHROMOSOMES 



Whether the maternal spindle attachment in a 

 particular bivalent goes to the ' North ' or the 



* South ' pole of the spindle (and vice versa) for the 

 paternal one is a matter of chance ; it depends on 

 which way up the bivalent has orientated itself at 

 prometaphase. There is no correlation between the 

 mode of orientation of one bivalent and another in 

 the same cell. Thus in Drosophila melanogaster witk 

 four bivalents all paternal spindle attachments will 

 go to the same pole once in 16 (2*) times, in female 

 Locusts and grasshoppers witk 12 bivalents once in 

 4096 (2^2) . while in man with 24 i^valents this event 

 will only happen once in 16,777,216 (2^^) times. 

 Exceptions to this rule occur under special circum- 

 stances in Sciara, Oenothera and Drosophila miranda. 



As in the case of mitosis the first part of anaphase 

 (during which the spindle attachments repel one 

 another) is followed by a period during which the 

 middle part of the spindle elongates so as to form a 



* stem-body ' and completes the anaphase separation 

 of the two groups of chromosomes. 



Telophase 



The telophase of the first meiotic division does not 

 differ in any important respect from that of an 

 ordinary somatic mitosis. The two telophase nuclei 

 may pass into a more or less complete resting stage 

 between the two meiotic divisions {interphase or 

 interkinesis) in which the chromosomes become 

 unfixable as in a somatic resting stage or they may 

 remain condensed and undergo no changes between 

 the anaphase of the first division and the metaphase 

 of the second (Fig. 10*). 



Second Meiotic Division 



If the chromosomes have not gone into a resting 

 stage during interkinesis (a matter which is subject 

 to a surprising amount of variation even in the same 

 organism under different conditions) there will natur- 



