CHAPTER VII. 



THE DEVELOPMENT OF THE OVUM OF THE FOETUS 

 FEOM THE OVUM OF THE MOTHEE. 



From the Ovum of one generation to the Ovum of the Next. 



— The manner in which the face, neck, pharynx and cutaneous 

 sbructures of the body are produced having now been traced, it is 

 necessary, before further progress can be made, to turn to the 

 phenomena which mark the opening stages in the development of 

 the embryo. This may best be done by following the cycle of 

 changes which lead to the production of a new generation of 

 germinal cells from the fertilized ovum of a former generation. 

 Every ovum is the offspring of a fertilized ovum, and the fer- 

 tilized ovum is the intermediary whereby the characters and 

 properties of a race are handed from one generation to the next. 



Descent of the Ovary. — In the female human foetus of the fifth 

 month the ovary has reached the iliac fossa (Fig. 59) in the course 

 of its descent from the lower dorsal region where it originated to 

 its permanent position on the lateral wall of the pelvis. The ovary 

 is then long and narrow, with an upper and lower pole ; it is 

 three-sided in section — the surfaces being inner, outer and inferior 

 or ventral (Fig. 60). The Fallopian tube, derived from the upper 

 part of the Miillerian duct, lies along the outer side of the ovary 

 in the iliac fossa ; its upper fimbriated end terminates at, and is 

 attached to, the upper or cephalic pole of the ovary (Fig. 59). 

 As the parts lie on the iliac fossa, the tube and the ovary are 

 supported each by its own mesentery, the mesosalpinx and 

 meso-ovarium. The two mesenteries have, however, a common 

 origin or attachment to the posterior abdominal wall and to the 

 common attachment the name of common genital mesentery may 



