FERTILIZATION 



119 



1 



M 



cilia maintains its identity much longer and may be 

 distinguished throughout the early development of the 

 embryo, but it finally 

 merges with the proto- 

 plasm of the egg. 



As the sperm nucleus ^ 



moves toward the egg 

 nucleus, it enlarges some- f 

 what, and the two nuclei 

 soon come into contact 

 (Fig. 61). At the time :, 

 of contact both nuclei are 

 in the resting condition, I 

 and this condition con- ^- 

 tinues even after the 

 nucleus of the sperm has 

 become more or less 

 imbedded in that of the ^ 

 egg. From this point the 

 development must be ,^, 



exceedingly rapid, for the \ 



next stage observed 

 showed the division of 

 the nucleus formed by the ^' „ 



fusion of the two nuclei 



. , , Fig. 61. — Stangeria paradoxa, 



of the egg and sperm, the showing fertilization; the sperm 



first division in the nucleus is entering the nucleus of 



sporophyte generation. ^^^ ^s^: ^^^ ^pi^^l' ciliated band of 



rrv- , • Ml , ^ 1 the sperm remains at the top of the 



I his stage is illustrated „• ui -e. a 



° egg. Highly magnified. 



by Fig. 62 in the next 



chapter. The fact that this division, at the stage repre- 

 sented in the figure, shows only half the number of 



w'*1 



^1 

 ■1 





