MATURATION. 



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matocytes of the male. The egg now leaves the ovary and reaches the oviduct. 

 Jf the ovum is fertilized, another spindle forms and a second polar body is 



FiG.i4. Maturation of the ovum of Ascaris megalocephala (bivalens). Boveri, Wilson. A, 

 The ovum with the spermatozoon just entering at x* ; the egg nucleus contains 2 tetrads (one not 

 clearly shown), the somatic number of chromosomes being 4. B, Tetrads in profile. C, Tetrads 

 on end. D, E, First spindle forming. F, Tetrads dividing. G, First polar body formed, containing 

 2 dyads; 2 dyads left in the ovum. H, 7, Dyads rotating in preparation for next division. /, 

 Dyads dividing. K, Each dyad divided into 2 single chromosomes, thus completing the reduction, 



given off. The nucleus of the mature ovum or female pronucleus, with the 

 haploid number of chromosomes, is now ready for union with the male 

 pronucleus. 



