MASTIGAMCEBA ASPERA. 71 



narrower, and generally pellucid. 

 of the pseudopodia, in this aspect of the animal, is 

 fairly regular : they extend outwards from the margins 

 of the compressed body, being, in fact, extensions of 

 the ectoplasm, and appear to occupy a common plane. 

 The refringent character of the ectoplasm extends also 

 to the pseudopodia, and is heightened by the presence 

 of innumerable minute spiculae which adhere to the 

 surface tangentially or horizontally. The nucleus is 

 single, imbedded in the anterior ectoplasm just behind 

 the frontal lobe, and is sometimes hidden by the semi- 

 opaque granular endoplasm. From this lobe the 

 flagellum extends outwards, its point reaching beyond 

 the extremities of the pseudopods ; it is hyaline, very- 

 refractive, and always alert, moving and coiling with 

 great rapidity ; from which circumstance it is not in- 

 frequently difficult of detection. Contractile vesicles, 

 usually two, on opposite sides of the body, in the 

 posterior region. 



Dimensions variable: length averaging 1 50-200 /x; 

 average breadth about 50 p,. 



In the ooze of ponds, and amongst floating vegeta- 

 tion, at Chelford and Xorthenden, Cheshire ; and at 

 Fearnhead, Lancashire. 



The facial aspect of Ma stig amoeba aspera differs 

 remarkably from that of the larger Amoebae, with which 

 it might be confounded. It attracts attention at once 

 by its refringent protoplasm. The flagellum, its pecu- 

 liarly-distinctive feature, is stated by F. E. Schulze to 

 be 0*06-0*08 mm. long, and is rightly described by 

 him as " a very fine filament of equable but hardly - 

 defineable character, and considerable refractive po \ver." 

 It is not attenuated at the extremity but of equal 

 thickness throughout, and ends " as if abruptly cut off." 

 The movements of the animal are distinctly amoeboid ; 

 the action of the flagellum has no effect as an organ of 

 locomotion, though in very young and small indi- 

 viduals its rapid movements do seem at times to 



