REGENERATION IN VERTEBRATES 299 



the electron microscope (Figures 1 and 6). Epidermal cells were 

 readily identified by, among other criteria, the thickened adhesion 

 plaques characteristic of attachment zones between epidermal cells. 

 Vacuoles were present, ranging in size from occasional large ones that 

 distorted the nucleus to numerous minute ones. Debris in various 

 states of dissolution was seen within many of the vacuoles. Red blood 

 cells and wandering cells packed the intercellular spaces, and some 

 of the inclusions within the epidermal cells resembled fragments of 



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Figure 6. Electron micrograph illustrating great phagocytic powers of epi- 

 dermal cells. It shows parts of basal epidermal cells and subepidennal 

 region (G) ten days after infusion with 0.03 molar beryllium nitrate into a 

 moderate early regenerate amputated ten days previously. Cells contain in- 

 clusions and debris in various stages of dissolution, some being obviously 

 within vacuoles (V). Note large vacuole in upper cell compressing nucleus 

 ( N ) . Smaller one near it appears to contain a fragment of an erythrocyte 

 (R). Note erythrocyte (R) in subepidermal region (G). Note also extrusions 

 of basal cytoplasm (E). Fixative: osmium tetroxide. Magnification: about 

 3,000 X. 



