DEVELOPMENT OF WANDERING MESENCHYMAL CELLS 533 



of more irregular shape with short amoeboid processes. Figures 3 

 and 4 show the cells highly magnified and in active movement; 

 figure 3 the spindle-shaped delicate process type and figure 4 

 the heavier more amoeboid cell. These cells are actively wander- 

 ing and changing in shape as figure 4 shows. From A to E are 

 the outlines presented by a single cell at five minute intervals. 



Fig. 1 A group of mesenchyme cells indicated in outline, camera lucida sketch, 

 wandering out from the side of an early embryo, 45 hours old. Two kinds of 

 cells are seen, one with delicate filamentous processes and another amoeba-like 

 cell. 



Fig. 2 A similar group in one microscopic field from an embryo 48 hours old, 

 again showing the two types. The elongate spindle cells are future endothelial 

 cells. 



