MATURATION 355 



mammals, but in some — e. g. the rabbit, cat — only as the 

 result of copulation. Failing copulation in these animals 

 the follicle undergoes atrophic changes. Upon the discharge 

 of the ovum the fimbriae of the Fallopian tube are erected 

 around the ovary, and by their muscular and cihary action 

 sweep the ovum into the tube. 



While these changes are taking place the ovum undergoes 

 the process of maturation. The ovum divides by karyo- 

 kinesis, the cleavage being very unequal. The smaller 

 product is extruded upon the surface of the ovum and is 

 known as the first 'polar body. This may later divide into 

 two. The ovum then forms a second polar body, but in 

 this division the number of chromosomes is reduced by 

 a half. The nucleus of the matured ovum is known as 

 the female jjronucleus. 



The process of maturation may be thus represented : — 



OOaONIUM % 



i 



PRJMARy OOCYTE 

 OR OV^UM 



SECONDARY __^ _. 



OOCYTE. ^H^ ^ F/RjST POLi^R. BODY 



[HETEROTYPL 

 \ DIVISION 



M/9 TUR.E 

 OVUM 



-POLAR. BODIES 

 Fig. 06. — Maturation. Compare with Fig. 64, p. 348. 



In the male all four products of division become 

 functional reproductive cells ; in the female this happens 

 only to one, the others playing a subsidiary role. 



