PLATE 3 



EXPLANATION OF FIGURES 



20 to 26 Small eosin staining bodies (degenerating erythrocytic nuclei) in 

 the coelomic cavities, some of which contain variable quantities of basophilic 

 material in the form of small spherules and peripheral rings. 20, 22, 24, 26 are 

 from the pleural cavities of 7 mm. pig embryos; 21, 23 from the pericardial cavity 

 of a 13 clay mouse embryo, and 25 from the pleural cavity of a 9 mm. pig embryo. 



27, 28 Ring form structures (degenerating erythrocytic nuclei) in the tissue 

 spaces. 27 is from the mesenchyma of the ventral thoracic wall of 9 mm. rabbit 

 embryo and 28 from the gasserian ganglion of a 13 day mouse embryo. 



29, 30 Degenerating erythrocytic nuclei in the heart cavity of a 7 mm. pig 

 embryo (29) and of a 13 day mouse embryo. 



31, 32, 33 Groups of small bodies, e (degenerating erythrocytic elements con- 

 sisting chiefly of nuclear material) in the embryonic tissues. 31 is from the 

 mesenchyma of the ventral wall of a 9 mm. rabbit ; 32 from the mesenchyma the 

 septum transversum of a 7 mm. pig embryo; and 33 from the ventral wall of the 

 fore-brain of a 13 day mouse embryo. Shows their variation in size, structure, 

 stain reaction and intercellular relations. 



34, 35, 36 Ring form nuclear structures (Cabot's rings) observed in degen- 

 erating erythrocytes found in the embryonic circulation. 34 and 35 respective- 

 ly, are from a small blood vessel in the mesenchyma and a sinusoid in the liver 

 of a 13 day mouse embryo; and 36 from a blood vessel (or posssibly lymphatic) in 

 the mesenchyma of a 9 mm. pig embyro. 



37 Erythrocytes in the hepatic sinusoid of a 13 day rabbit embryo showing 

 earlier stages in degenerative nuclear and cytoplasmic changes including lobula- 

 tion of nuclei, hemolysis and cytoplasmic vacuolation. 



38 Cells found in the intercellular tissue spaces of the mesenchyma of the 

 same embryo as for figure 37, concerning which grounds were advanced in the 

 text indicative of their degenerating erythrocytic nature rather than leucocy- 

 tic elements differentiating in situ from mesenchymal cells. 



39, 40 Cells from the mesenchyma which appear in nuclear and cytoplas- 

 mic structure clearly intermediate between the cells shown in figure 38 and the 

 degenerating erythrocytes in figure 37. From the same source as figure 38. 



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