24 



MATUEATION OF OVUM 



FIG, 83. STAGES OF MATUBATION, EGG or ECHINUS ESCULENTUS. x 1200 diameters. (T. H. Bryce.) 



a, Prophase of heterotype : double chromosomes ; &, metaphase of heterotype : separation of 

 chromosomes I. and their commencing secondary cleavage; c, anaphase of heterotype: completion of 

 secondary cleavage : extrusion of first polar body ; d, prophase of homotype : chromosomes pass 

 unchanged into second polar spindle ; e, metaphase of homotype ; /, anaphase of homotype : separation 

 of chromosomes n. : extrusion of second polar body. 



