PLATE 4 



EXPLANATION OF FIGURE 



31 Ventral view of the lower half and right side of the reconstruction repre- 

 sented in figure 30 (23 mm. pig. embryo, series 23a, J.H.E.C, from section 12, 

 slide 25 to slide 30 inclusive) , X 50. 



5d, extremity of the injected portion of 6b, postcardinal veno-lymphatics 



the right thoracic duct 7, posterior portion of the oblique 



X, blind end of 5d and the farthest vessel and its junction with the post- 



extent to which the injection mass cardinal 



has penetrated 8, dorsal segmental veins 



4d, discontinuous and uninjected lym- lid, right postcardinal vein 



phatic spaces in the right thoracic 12d, right supracardinal vein 



duct line IS, aorta 



32 Sinistro-ventral view of the lower third of the reconstruction shown in figure 

 31 (19 mm. pig embryo, series 168, slides 22-24 inclusive), X 50. 



6c, periaortic supracardinal veno-lym- 12s, left supracardinal vein 



phatics 20, right mosonephros 



lis, left postcardinal vein 



33 Reconstruction of a segment of the anterior supracardinal division or region 

 of the periaortic veno-lymphatics in a 22 mm. pig embryo (series 105, slides 34-36 

 inclusive), X 50. Dextro-ventral view. 



4d, 4-s, lymphatic spaces replacing the degenerating veno-lymphatics (6c). Other 

 explanations the same as above. 



34 Reconstruction of the same region, represented in the preceding figure, 

 in a 23 mm. pig embryo (series 67, slides 36-37 inclusive), X 50. Sinistro-dorsal 

 view. 



5, right and left thoracic duct; veno-lymphatics have been completely replaced. 

 Other explanations the same as above. 



472 



