RECENT MEMOIRS ON FRESHWATER RHIZOPODA. 363 



but they noticed the homogeneous character of the median 

 region as distinguished from the granular outer pait bear- 

 ing the green or colourless corpuscles ; they noticed also 

 the contractile (but non-protuberant) vacuoles in the outer 

 region, although GreefF has not seen their contraction. 

 I had long overlooked the nucleus, — carmine fluid readily 

 indeed discloses it. Hertwig and Lesser more correctly de- 

 scribe it. Gretiacher overlooked it, though GreefF disclosed 

 it by pressure, but without arriving at a sense of its nuclear 

 nature. The latter author speaks of certain " manifestly 

 cellular structures "^ which, so far as I can see, Hertwig and 

 Lesser very correctly deny, and refer what met Greefl's obser- 

 vation to simple vacuoles. Moribund or half effete sarcode 

 of many forms is in fact prone to form " vacuoles " sur- 

 rounding some of the granular structures or corpuscles, 

 simulating the appearance of " cells " with '' nuclei." 



Grenacher records the observation of " a rather large cavity 

 of irregular contour, apparently filled witha watery fluid, which 

 assumed a stellate figure whilst producing sinus-like inlets 

 of the plasma." . . . . " Precisely in the centre of this cavitv 

 there occurred without exception a little j^ale corpuscle, 

 whence numerous, likewise pale threads run out like rays 

 in all directions.''^ These fine radiating lines Grenacher 

 regards as prolongations of the (presumed) axile threads 

 of the pseudopodia. Greeff believes he has found the same 

 structure.^ He speaks of" a clear round or oval vesicle almost 

 in the centre of the Acanthocystis from which the re- 

 markable stellate radiating-system of fine threads proceed." 



This peculiar central structui-e in A. turfacea Hertwig and 

 Lesser have been unable to detect ; that so able observers 

 have not succeeded in refinding it I almost feel glad, for 

 I as yet have not been able to see it. But the opaque cha- 

 racter of this form, so densely loaded as it is with green 

 and dark granules, is well calculated to prevent an observa- 

 tion in this regard. The nucleus, however, is not difficult 

 of detection, once one knows it is there. See, however, 

 Schulze's description hereafter of quite a similar internal 

 structure in his Raphidiophry s pallida. 



Hertwig and Lesser record: — Certain examples of this 

 species, otherwise normally develoj)ed, presented themselves 

 more or less closely covered externally with colourless, very 

 refractive, globular bodies, about equal in size to the chloro- 

 phyll-granules. These shining bodies were laid closely about 



' Loc. cit., pp. 290, 292, 293. 

 2 Loc. cit., p. 490. 

 ' Loc. cit., p. 487. 



VOL. XVI. NEW SER. A A 



