420 



OTTO F. KAMPMEIER 



Fig. 2 Transverse section taken near the level of the left Cuvierian duct in 

 a 17 mm. embryo (series 167, slide 15, section 22), X 100. 6a and 7 (oblique vessel), 

 precardinal veno-lymphatics located in the positions of the later right and left 

 thoracic ducts respectively; 8, dorsal segmental vein; 10, left precardinal; lid, 

 right postcardinal; 12ld, 12ls, right and left supracardinal lines; 13, aorta; 14, 

 sympathetic nerve trunk; 15, vagus; 17, oesophagus; 18, trachea. 



stages of the thoracic duct history. In figure 2, 21 it (7) is illus- 

 trated in section, taken just in front of its junction with the 

 middle segment of the right supracardinal line, which in this 

 embryo (17 mm.) had not yet fused throughout its entire extent 

 with the right postcardinal. 



21 The image of the sections being reversed by the microscope lens, the structures 

 of the right side of the embryos are seen on the left side in the microphotographs, 

 and vice versa. However, in the dorsal views of the reconstructions and in figure 

 13 the right and left sides correspond with the respective sides of the page. 



