The Selachian yolk-sac placenta system is illustrated here with nearly full-grown 

 foetuses {Mustelus manazo). Note the umbilical-like connection between the foetus 

 and the placenta, a system which approaches— but is not exactly the same as— the 



mammalian placenta. Courtesy, Einar Munksgaard from 



Danish Scientific Investigations in Iran, 1944 



238 



