Figs. 2 to 11 Successive drawings of the same region (A in fig. 1) in the fin 

 expansion of the tail of hyla pickeringii larva, to show the relation between the 

 growing lymphatics and the growing mesenchyme cells. Drawings were made 

 while the larva was anesthetized with chloretone. The individual mesenchyme 

 cells, A to Z and 2 to 20, are represented by three forms; solid black: cells near 

 the surface, toward the observer; cross-lined: cells in interior; dotted: cells near 

 the surface away from the observer. The same letters in the different drawings 

 indicate the same cells. Where a cell has divided the two daughter cells are 

 indicated as B 1 and B' 2 . Between figs. 9 and 10, also between figs. 10 and 11, 

 records were made nearly every day, which have not been reproduced, which show 

 the intermediate positions of the cells and of the lymphatic. Lymphatic wall, 

 Lym LL, is represented as somewhat thicker than it actually is. The nuclear 

 areas in the lymphatic are represented by dots. In figs. 4, 5 and 6 the three cells 

 shown B, J and A', are the ones in approximately the same layer as the lymphatic. 

 Fig. S is included because it shows well the wandering into the sprout of a nuclear 

 area (nucl), from the main stem. In figs. 4 to 7 this nuclear area is seen just start- 

 ing into the sprout. Enlargement 300 times. 



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