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THE AMERICAN NATURALIST [Vol. XL 



animal and the amount and form of the food. When the food 

 vacuole contains rounded bodies like Chlamydomonads the cyst 

 is spheroidal in form (Figs. 5 and 6). One animal was seen 

 encysted about a single Navicula sp. In tliis ciisc the cyst was 

 oval (Fig. 4); in Fig. 2 is shown an encysted individual which had 



a food vacuole of numerous long bodies that determined an elon- 

 gated cyst. The animals Ya,ry greatly in size. Fig. 1 represents 

 an individual that is somewhat larger than the average; the cysts 

 of course are found to vary as greatly in size. 



Upon encystment the animal is colorless or nearly so (Fig. 5). 

 During encystment a color is assumed in some cases, which seems 

 to depend upon the character of the food that is being digested. 



