CHAPTER I. 



or nn: 8MXUAL rnoni < 

 -CELL ANI> SI:MI.\-( i i i .. 



IN most animals, and without except ion in ail V i thf 



development of a \u-\\ heinir t"m take plan- (.nly wh- n reprodu. 



elements, product d liy two sexually dill' n lit indi\ iduals, the egg 

 liy tin- female, and tin- seminal corpu>cle or seminal lil.-iiin nt 1>\ 

 male. arc at t IM- proper 1 imc lrouirlit into uni'.n aNtln- n >ult of 

 tin- procivMtivf act. 



Tin >'</;/ <ui<ltlt>> fifim'iHil Jt/tnin/if <ir>' sinifil' </>,/< nt<ir>i /'//> /,/ ' 

 which an- |ii-oiliu'nl in special glandular ori, r :nis. tin- egg-Oellf in th- 

 OVary of the }'. male, and the scm. n-cdls in tin- testis of tli- male. 

 After the le^i, in i]| U ,,f sexual maturity at delinite ( >eri ( ,d<, th.y 

 detach theinsel\- s \vit liin t In- sexual .'Tirans from their union with 

 the n mainiiiLT cells of the body, and form, under Miitahle condi' 



of development, among which the union of the two sexual oeJ 



the most imjtoi tant, the starting point fora new OTganiBOL 



l-'irst of all, thei'fore. \\e have to acquaint ourselves with tin 

 pt culiarii i< > of the t wo kinds of sexual pndu< 



1. The Egg cell. 



The et:i: is l>y far the lario st c-ell of the animal lnly. At a t 

 when nothing was known of its cell nature, i mponents 



given special names, whieb remain in D 



time. Theconteiitx were Call) d 1 nucl. us 



was call* d VttlCula <j> rmiit'i rminative v >icle. l by 



the phy.-siolo.ri>! Pi KKIN.II: ; thi-nucleai corpuscles, or nm leoli. wore 

 calh d irerminative sp. 



linally, the c t ll-m niln aiie \.;.s i-alli il t In- yolk niemhraiie. ,r /,,.,,,- 

 Itrima citt'llinti. All ti y in no! nnimpoi taut ways from 



