OVULATION AND 

 MIGRATION OF EGG 

 TO AREA WHERE 

 FERTILIZATION 

 IS TO OCCUR 



SPERM DISCHARGED 

 FROM T ESTI S AND 

 MIGRATE TO AREA 

 WHERE FERTTLI Z ATION 

 IS TO OCCUR 



PRIMARY ^^ 

 PHASE OF 

 FERT ILIZATION, 

 I E .ACTIVATION 

 PROCESSES 

 AROUSED IN 

 EGG AND 

 SPERM WHICH 

 BRING ABOUT 

 THEIR CONTACT 



GYNOGAMIC 

 SUBSTANCES 

 SECRETED INTO 

 SURROUNDING 

 FLUIDS FROM 



THE EGG. 

 MATURATION 

 DIVISIONS 

 INITIATED IN 

 CERTAIN EGGS 



MOTILITY 



STIMULATED 



ANDROGAMIC 



SUBSTANCES 



SECRETED 



/ 



> 



SPERM STIMULATED 

 TO GREATER 

 ACTIVITY AND 

 ATTRACTED TO 

 EGG BY GYNOGAMIC 

 SUBSTANCES 



SPERM SECRETIONS 

 AID SPERM IN 

 REACHING EGG 



SECONDARY 

 PHASE OF "~ 

 FERTILIZATION 

 IE, ACTIVATION 

 PROCESSES 

 AROUSED 

 IN EGG AND 

 SPERM WHICH 

 RESULT IN 

 FUSION OF THE 

 GAMETES 



MATURATION DIVISIONS OF EGG 

 COMPLETED AND SPERM DRAWN 

 INTO EGG;SPERM NUCLEUS EN- 

 LARGES AND ASTER FORMS IN 

 MIDDLE PIECE OF SPERM 

 FERTILIZATION MEMBRANE DEVE LOPS 

 AND PERIVITELLINE SPACE AND 

 FLUID APPEARS BETWEEN EGG 

 AND MEMBRANE IN SOME SPECIES 

 (AMPHIOXUS) , IN OTHER SPECIES 

 PERIVITELLINE SPACE AND FLUID 

 FORMS BETWEEN EGG AND 

 PREVIOUSLY FORMED MEMBRANE 

 (FISH, FROG, MAMMALS) , EGG MAY 

 CONTRACT SLIGHTLY WHEN 

 PERIVITELLINE FLUID FORMS; 

 OOPLASMIC SUBSTANCES 

 MIGRATE TOWARD POINT WHERE 

 SPERM HAS ENTERED (FROG, 

 AMPHIOXUS , AND STYELA) 



FUSION OF PRONUCLEI 

 AND ESTABLISHMENT OF 

 NEW DIPLOID CHROMOSOMAL 

 COMPLEX ; CLEAVAGE 

 AMPHIASTER FORMS 



COMBINATION OF ACTION 

 OF GYNOGAMIC SUBSTANCE 

 AND ANDROGAMIC 

 SUBSTANCE POSSIBLY 

 BINDS SPERM TO EGG 

 SURFACE AND IMMOBILIZES 

 SPERM 

 GAMETES NOW READY TO 

 BEGIN SECOND OR FUSION 

 STATE OF FERTILIZATION 



OOPLASMIC MOVEMENTS 

 OCCUR, RESULTING IN 

 REORIENTATION AND 

 SEGREGATION OF DEFINITE 

 OOPLASMIC SUBSTANCES 



CLEAVAGE INITIATED 



Fig. 121. (See facing page for legend.) 



242 



