PLATE 12 



EXPLANATION OF FIGURE 



23 Drawn from a reconsti-uftion of a chick embryo of 6 days and 22 hours, 16 

 mm. (series 463). Mesial view. 



10, prccardiiial vein 15a, thoracic duct 'apiiroach' of jugular 



11, suhclavian vein lymph sac 



12, duct ofCuvicr 16, groups of developing blood cells 

 15. jugular lymi)h sac 17, rudiments of thoracic; duct, extreme 



cephalic end 



use. 



