68 THE CHROMOSOMES 



present, either closes up again, and is thus non- 

 functional, or else functions as the effective split at 

 the next division (in animals the first cleavage 

 division of the zygote, in Angiosperms the pollen 

 grain mitosis in microsporogenesis and the first 

 division of the embryo-sac nucleus in megasporo- 

 genesis). 



