230 PLANT LIFE 



persists are the chromosomes. These bodies, 

 as already indicated, take up a very definite 

 position, and now lie in an equatorial plane 

 half way between the two poles to which 

 the spindle fibres converge. 



Each chromosome then divides longitudin- 

 ally into two symmetrical halves, probably 

 along the line of the parallel streaks of chro- 

 matin described above. The two halves then 

 diverge, and the daughter chromosomes at once 

 retreat along the spindle fibres, to form two 

 groups, one at either pole. The daughter 

 chromosomes swell up, a nuclear wall is 

 formed around them, some of the substances 

 which escape from them run together and 

 form new nucleoli, and thus the two daughter 

 nuclei are formed. A cell wall is often de- 

 veloped across the spindle which persists for 

 a time between the two nuclei which have 

 thus been constituted, and nuclear division is 

 then followed by cell division. When the cell 

 wall is not so formed, a binucleate, or later 

 a multinucleate, arrangement is produced. 



The main conclusions that emerge from a 

 consideration of the facts thus briefly out- 

 lined are : (1) The number of the chromo- 

 somes is constant, and individual peculiari- 

 ties in form and size are seen to reappear 

 whenever the chromosomes are sufficiently 

 contracted as to become sufficiently clearly 

 recognisable. (2) The chromosomes, when 

 they divide, transmit their peculiarities to 

 each daughter chromosome. In other words, 



