558 - Heredity and Evolution 



Fig. 29-3. Human embryos: A, 26 days after ovulation (note particularly the gill slits, yolk sac, 

 and tail). B, 34 days (note the limb buds, eye, and brain). C, 43 days (note the well-developed 

 face and limbs and the umbilical cord). D, 56 days. In A, the magnification is some five times 

 greater than in D. (Courtesy of Dr. G. W. Corner, Carnegie Institution of Washington.) 



human blood; while the bloods of New strated (Fig. 29-5); similarly all birds are 



World monkeys and lemurs (Fig. 29-4) show found to have a fairly close relationship to 



a less and less intimate relationship. In this each other, and more distant ties to members 



way many degrees of relationship between of the reptile group (Fig. 29-6). All in all, 



the bloods of all mammals can be demon- more than a thousand animals, in several ilif- 



