Nos. 451-452-] STL/DIES ON THE PLANT CELL. 



5«7 



The subject of fertilization is reserved tor the next section 

 (Section IV) of this series and the present account will deal 

 only with the structure of the unfertilized ej^R. As the sperm 

 is derived from a motile ^^amete identical with the zoospore, so 

 the egg has had a similar origin. We have traced the stei)s in 

 this evolutionary process among the alga: m a tornier i)a])er 

 {Popular Science Monthly, Feb. 1903, P- 1>^^)- '^^^"^ '""^^ 

 cation of a differentiation in the sex of pnnutive gametes is one 

 of size. The male gametes tend to become smaller while the 



female ^^7' oj'^' ''^^ \Tni7n n^"^''^''^^ ^liit ' 1^ '1 '^'^^ ^tl^^ 



great many more mitoSL-> in antiuTidui in. in 111 M.,;;nii,a and con- 

 sequently a given amount <it prMtnphism ni;!>t be \ri> muc 

 divided to provide each nucleus with it> (juota '-1 i_\topla>m. 



The tendency of oogenesis on the lontrary i> to o-n.eive the 

 protoplasm for relatively few nuclei, i)io\ idc(l tor scx era! egg> or 



egg cell is generally richly sui)plied with j^rotoplasm. Such i)roc- 

 esses result in large cells with a i)roniinent c hromatophore or 



