338 



GYMNOSPERMS 



Two spindles are formed, which soon come together and appear as 



one. 



The most unexpected feature in his account is that the chromo- 

 somes become paired (fig. 329). In this diagram, only two of the 16 

 chromosomes of each gamete are shown. The chromosomes of the 

 egg nucleus are shown in black, and those of the sperm, in outline. 



Fig. 328. — Pimis laricio: union of two nuclei originally described as male and fe- 

 male, but which are, doubtless, the egg nucleus and the ventral canal nucleus. /, fe- 

 male; niy male. The chromatin is in the spireme stage; X500. — After Coulter.'''" 



The chromosomes of the egg and sperm pair, and then twist about 

 each other, as in the third and fourth figures of the diagram. They 

 then split transversely, giving rise to groups of four, which resemble 

 the tetrads of the reduction division (fifth and sixth figures of the 

 diagram). The distribution of the chromosomes then takes place as 

 shown in the final figure of the diagram. 



