REPRODUCTION AND HEREDITY 119 



were in the original nucleus. But as each primary oocyte 

 has only enough cell-substance to make one egg, the two 



Fig 32 —Diagrams of (a) normal cell-division (mitosis) with eight 

 chromosomes shown after splitting to form daughter-nuclei ; (6) matura- 

 tion of sperms (spermatogenesis), the primary spermatocyte divides 

 into two secondary spermatocytes (sc) with " reduced nuclei, and each 

 of these divides into two spermatids (s) ; (c) maturation ot egg 

 (oogenesis),/), ist polar body and pr 2nd polar body mature egg 

 ready for fertilisation, d, Maturation in a case where the full (diploid) 

 number of chromosomes is uneven, the sex chromosome {x) having no 

 partner. 



