PLATE 4 



EXPLANATION OF FIGURES 



8 From a section of a chick embryo of 6 daj's and 22 hours, 16.5 mm. 

 (series no. 464; slide XXII, section 22). Photomicrograph, X 133. 



1, aorta 16, groups of developing blood cells 



5, celiac artery 23, celom (pleural cavity) 



8, dorsal somatic artery 24, sympathetic nerves 



9 From a section of a chick embryo of 6 days and 16 hours, 13.5 mm. 

 (series no. 426; slide XVIII, section 3). Photomicrograph, X 233. 



1, aorta 17, lymph spaces, rudiments of thoracic 



16, developing blood cells duct 



23, celom (abdominal cavity) 



170 



