17 



than Powell and Lealand's third eye-pieceC, which is generally 

 preferred to all higher powers for accurate definition. 



When objectives are pressed to this extreme amplifica- 

 tion the jewelled brilliance of the translucent and radiant 

 beading vanishes ; they take a grey and sombre hue, and all 

 intervening structure is lost in an indefinable haze of exasr- 

 gerated aberration. The spherical beads of diatoms are 

 brilliantly transparent (being formed of pure silica ?) , and 

 they behave themselves in almost every respect as spherical 

 lenses, showing crescentic shadows, blending and mingling 

 with each other in endless variety, according as the inter- 

 spherical refractions develop single or multiple shadows. 

 I cannot refrain from expressing my convictions that all 

 diatoms of this character possess a double set of beading, set 

 in different planes. 



On some Freshwater Rhizopoda, New o7' Litti,e-Known. 

 By William Archer. 



{Continued from vol. ix, J^.S., p.S97.) 



Pleurophrys spherica (Clap, et Lachm.) ? PI. ? amphitremoides 

 (sp. no v.), and PI. ? fulva (sp. no v.) 



Having endeavoured in the foregoing to give some account 

 of the remarkable form, Diaphorojiodon mobile, I pass on to 

 the three others, Avliich in the present series seem next re- 

 lated thereto, figured on PI. XX, figs. 1, 2, 3 (vol. ix), and 

 which I would (provisionally at least) identify as above. I 

 regret, however, that I have it in my power, at present at 

 least, to do but very little more than refer to the figures and 

 the accompanying explanation of the plate. 



It will be seen by the appended notes of interrogation that 

 it is not without some amount of uncertainty as yet that I 

 refer these forms to Claparede and Lachmann's genus, w^hicli 

 is thus characterised : — " Body covered by a test furnished 

 with a single opening, and formed of foreign substances 

 agglutinated by means of an organic cement," to which dia- 

 gnosis is prefixed the remark that this genus is to the Acti- 

 nophryans as the Difflugiae are to the Amoeb8e.^ 



From this we are to understand that in Pleurophrys the 

 sarcode body emits slender linear, unbranched pseudopodia, 

 through the single aperture of a test formed of agglutinated 

 foreign particles. Nor must the figure given^ be misunder- 



' Ciaparede et Lachmann, 'Les Infusoires et les Tlh'zoponej:,' p. 15!. 

 ^ Op. cit., pi. xxii, fig. 3. 



VOL. X. NEW SER. B 



