REPRODUCTION IN ANIMALS 



205 



dages of the first and second abdominal segments of the 

 male are modified into copulatory organs for the transfer of 

 the sperm to the body of the female, where they are retained 



Fio. 113. Diagrammatic section of the human uterus with developing embryo. 

 The embryo (h) is suspended in a fluid-filled cavity (c) surrounded by the foetal mem- 

 branes (e) and by tissue (/) from the uterus itself. The sole path of communication 

 between embryo and mother is by blood in vessels passing up through the umbilical 

 cord (i), spreading out into capillaries in the placenta (6) and there coming into close 

 relations with the maternal blood supply. The openings of the oviducts (d) into the 

 uterus become closed during the development of the embryo, a, dorsal wall of uterus; 

 b, placenta ; c, fluid-filled cavity of amnion ; d, openings of oviducts (Fallopian tubes) ; 

 e, foetal membranes; /, uterine tissue; g, uterine cavity; h, embryo; i, umbilical cord. 



until egg-laying. In most terrestrial Vertebrates, including 

 Man, fertilization occurs while the eggs are still within the 

 oviducts, the copulatory organs transferring the sperm 

 directly to the terminal portion of the ducts from which they 

 make their way up to meet the descending eggs. (Figs. 67, 

 71, 72, 86.) 



