AMEIOSIS 



415 



division determines a regularity in the first and second division of 

 the cell. Abnormality depends on the fact that, as a rule, the 

 univalents can divide only once. They may lie on the spindle at 

 first anaphase without dividing ; or having come on to the equator 



Fig. I 28a. — Possible courses of meiosis in the total absence of pairing. 



and divided at the first anaphase quickly enough to be included in 

 the daughter nuclei, they may be unable to divide again, and 

 consequently lag on the spindle at second anaphase. These lie 

 cross-wise at first and are pulled lengthwise later by the stretching 

 of the spindle (Mather, 1935). In either of these cases they may 



