SPERMATOGENESIS 



REPRODUCTION AND DEVELOPMENT IN CHORDATES 



OOGENESIS 



Primordial Germ Cells 

 (undifferentiated) 



Period of Division 

 (mitosis) 



Growth Period 

 (synapsis and tetrad formation) 



First Meiotic Division 



(disjunction of reduplicated 



homologous chromosomes) 



Second Meiotic 



Division 



(separation of 



chromatids) 



Mature 



Germ Cells 



(gametes) 



Spermatozoa 



Ovum 



Fig. 5.7. Garnet ogenesis in animals; diagrammatic. Homologous chromosomes are lettered alike; 

 A and B are autosomes, X and Y are sex chromosomes. The chromosomes shown in black repre- 

 .sent the paternal contribution; the unshaded ones are maternal in origin (p. 142). During 

 the growth period food is stored in the cytosome of the primary oocyte; this yolk remains in 

 the ovum and is not distributed to the polocytes. 



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