MEMOIRS. 



Resume of Recent Contributions to our Knowledge 

 of " Freshwater Rhizopoda." Part IV. Compiled 

 by Wm. Archer, F.R.S. (With Plate XIII.) 



Lecythium liyalinum, Hertwig et Lesser^ (Plate XIII, 

 figs. 1, 2), 



is the name applied to a form identified by the authors as 

 equivalent to that named Gromia kyalina by Schlumberger,* 

 and by Ehrenberg and Presenilis^ called Arceilla hyalina, 

 and again by Schneider identified as Diffiugia enchelys. No 

 doubt these authors were each wrong in referring such a 

 form to any of these genera. For that reason, seemingly, 

 Hertwig and Lesser conceived they were compelled to insti- 

 tute a new genus, therefore named as above ; Cienkowski* 

 accepts this genus. But it occurs to me to suggest that, just 

 as in Schulze's form referred to Gromia (as G. granulata), 

 there is little, if anything, to separate either from the genus 

 Plagiophrys, Clap, et Lachm. The test of Lecythium hya- 

 linum, Hertwig et Lesser, is roundish, pellucid, membranous 

 (structureless), thin — according to Hertwig and Lesser not 

 flexible, but according to Cienkowski it is flexible — accord- 

 ing to the former bilaterally symmetrical, but according to 

 the latter only accidentally so, with a short neck. The 

 body-mass completely fills the test, anterior portion granular 

 and vacuolar, posterior homogeneous and bearing a nucleo- 

 lated nucleus ; pseudopodia filiform, homogeneous, much 

 branched, sometimes anastomosing. (See fig. 1, showing a 

 dorsal or posterior view. Fig. 2, after Cienkowski, perhaps 

 doubtfully identical, shows a lateral view.) There seems 



1 Loc. cit., p, 117, t. iii, f. 8. 



^ Sclilumberger, ' Ann. d. Sc. Naturelles/ iii ser., vol iii, p. 255 (1854). 



3 Freseuius, ' Abhl. d. Seuckenb. Gesellsch.,' Bd. ii (1858). 



* Loc. cit., Bd. xi, p. 117 to vi, f. 5, 6. 



VOL. XVII. NEW SER. O 



