RHIZOPODS. 125 



and capture food as in the naked Rhizopods. When they 

 are withdrawn, the shell appears like a dead thing, 

 and may be rolled about the slide at the will of the 

 observer, or at the mercy of the currents. But often 

 while the student is looking at an apparently dead 

 shell of sand,, a blunt little wave of colorless proto- 

 plasm issues from the mouth, lengthens and narrows, 

 is followed by another and another, until the shell is 

 raised and moved slowly away, one of the most re- 

 markable of microscopic creatures. 



There are several species of the genus Diffliigia, of 

 which the following are among the commonest. They 

 are found abundantly on the mud and among the leaves 

 of Sphagnum. 



I. Shell pear-shaped (Fig. 97), without spines, al- 

 though the summit may be. prolonged into one or 

 two points; usually formed of sand-grains, some- 

 times with adherent diatoms; occasionally formed . 

 entirely of diatoms; mouth at the narrow end, 

 circular, smooth, without teeth or lobes. 

 The body within the shell is usually green, some- 

 times colorless; pseudopodia colorless, thick, 

 blunt. The animal is .almost as fond of the cellr 

 contents of Spirogyra as is Vampyrella, and ob- 

 tains them in a similar way; but instead of appear- 

 ing to suck them out of the cell, Diffliigia pyrifdr- 

 mis pierces the wall, inserts its pseudopodia, with' 

 them surrounding the color-bands and other cell- 

 contents, lifts the entire mass out and passes it 

 into the body within the shell. I have seen a sin- 

 gle Difliugia empty four Spirogyra-cells in suc- 

 cession. This species is common. Diffliigia 

 J>yrifdrmis, Fig. 97. 



