DIFELUGIA CONSTEICTA. 57 



position of which is always excentric ; the structure 

 rounded posteriorly, and sometimes furnished with 

 two or more spines (curved or straight) as in Gentro- 

 pyxis. The moiith circular or oval, its edges more or 

 less inverted, with the anterior lip prominent. The 

 chitinous test coloiirless, yellowish, or brown, and 

 covered with irregular scales, large and small inter- 

 mixed, or with sand-grains or other extraneous 

 particles. Plasma-body transparent, colourless, or 

 crowded with small yellowish or greenish granules. 

 Pseudopodia normal. 



Dimensions: Variable [; 30-125 ju, (Penard)]. 



In the ooze of ponds;' in marshy ground, and on 



66 67 



Fias. 66 AND 67. — Lateral views of Difflugia constricta. x 'dOO. 



moist rocks, amongst Sphagnum and other aquatic 

 mosses ; extremely common. 



This is one of the most variable of the JDiffiugiee, 

 and the limits of the species are by no means well- 

 defined. Between an example figured (PI. XIX, fig. 18), 

 which is the largest as well as the most perfect we 

 have met with, and the minute 8phagnum-\o\mg 

 forms, there is every possible gradation. Some spined 

 varieties indeed approach so closely to Gentropi/xis 

 aculeata in form and general structure, if not in size, 

 as to suggest an affinity between them ; but it would 

 hardly be safe to say that they are connected by a 

 series of intermediate forms. 



The species is cosmopolitan and it is more than 

 probable that its variable character is induced by the 

 surrounding conditions. Ponds may be said to yield 



