RECENT MEMOIJIS ON FRESHWATBR RHIZOPODA. 343 



the pale-bluish granules of every granular plasma, occur tlie 

 here characteristic ones ; this central substance further shows 

 a greater or less number of irregularly oval-figured bodies, 

 varying from a greenish-brown to a reddish-brown tint. 

 These the authors regard as manifestly more or less assimi- 

 lated food-substances of vegetable origin, becoming more and 

 more reddish the more they have become digested. This 

 coloured region further possesses a number of vacuoles, 

 sometimes difficult to be made out owing to the opacity of 

 the body-substance. The authors were unable to determine 

 if these were contractile, an observation, indeed, rendered 

 the more difficult owing to the constant rolling movement of 

 the organism, causing a vacuole brought under view to be 

 the next moment withdrawn from observation. 



The general opacity of the form rendered a critical exami- 

 nation of the nucleus impossible, but the presence of this 

 body, of ordinary character, was rendered evident by appli- 

 cation of acetic acid and subsequent pressure. 



The foregoing curtailed description applies to the ordinary, 

 that is, the flat, view of the organism as obtained from above. 

 The authors sometimes succeeded in obtaining a profile view 

 as it crept along the surrounding objects. They were then 

 able to see that the lower part of the animal, sometimes 

 smooth, sometimes bent, adapted itself to the conditions of 

 the surface on which it moved, whilst the, so to call it, 

 dorsal side formed a hump-like elevation. This elevation is 

 formed of the coloured granules, and, according to their 

 position, as seen from above, it appears sometimes median 

 and sometimes at the hinder end. Sometimes this elevation 

 is steep, explaining why sometimes the median region, as 

 seen from above, appears so sharply marked off from the 

 hyaline border. This latter, in this side view, is seen to 

 encompass the organism above and below. 



The most remarkable, and also characteristic, feature of 

 this form is its mode of locomotion. Still less than in an 

 Amoeba this is effected without the aid of pseudopodia ; only 

 a very slight alteration of contour, with the slightest possible 

 wave-like expansions occur, too slight, the authors think, to 

 account for the movement of this sarcodine. By the appli- 

 cation of higher powers the authors made out that the pro- 

 gression was effected by a revolution or rolling move- 

 ment of the whole body, so that each point of the superficies 

 comes to be in a constant rotation, by virtue of which it 

 advances from the posterior end forwards to the anterior, 

 and then to the " ventral," and so on, like a wheel. This 

 action can be the more readily seen by watching certain 



