H U i ' fio: 



S ' '"' ' ^^ 



?t - '*, \ v ? ^ * 



t .-' -'- i ^A , & 



vJw/WZi *^VT? 



._---; --:- I"^',.*! 



; l-r^ 

 ^ --"O^p 



j-V ~.~. \~ C^^.mi: 



;^s 



?+-: .,"\ feSSSS 



vy-^r- . ... d 



grf 



"<^ 



; J 



si 



ro/ . 



^" " - -" - ' . * - r 



ar*n 



* ' 



*5 



,' -" ^* 



; "*< . 



.. ' .---! - 



% ""-' 



^. ^ 



K L 



F, Appearance of the definite centrosome. G, H, Division of the 

 centrosome. 



(In c-H the arrow marks the direction of entrance of the spermatozoon.) 



i, Approach of the two pronuclei. Formation of spindle-fibres. 



J, Formation of asters, elongation of spindle, further enlargement of 

 pronuclei, and appearance of chromosomes. 



K, Further elongation of spindle, and formation of a centrosphere 

 round each centrosome. The pronuclear membranes are breaking down 

 and the spindle-fibres passing in. 



L, The fully-formed fertilization spindle. In the equator are the chromo- 

 somes, now longitudinally split, and attached to large spindle-fibres. In 

 each centrosome the centriole has divided. 



