RECENT MEMOIRS ON FRESHWATER RHIZOPODA, 121 



no particular season ; in Microgromia Hertwig found them in 

 spring, Cienkowski late in autumn. 



It is quite unnecessary here to dwell on the manifest 

 generic distinctions of this form from the other Monothala- 

 matous monostomatous Rhizopoda — such as Euglypha, 

 Cyphoderia, Trinema, Plagiophrys, Lecythium, Pleurophrys, 

 all again so distinct inter se. So distinct indeed j9e?' se does the 

 rhizopod forming the type of the genus Microgromia appear, 

 that so far as I am concerned I cannot at all recognise this 

 species in the form alluded to, and figured by Schulze^ 

 and called by this name. The form here in question [M. 

 socialis) can by no means be one and the same with '' Dif- 

 flugia Euchelys," Ehrenb, or '" Arcella hyalina" Ehrenb. The 

 most prominent distinctions at first glance are the close ap- 

 plication of the body-mass to the test all round, and the long 

 straight but very slightly branched non-granuliferous pseu- 

 dopodia, and no pulsating vacuole — distinctions which I can- 

 not doubt carry with them essential deep-going specific, even 

 generic, differences. The form no doubt seems to be " social " 

 in habit, but this Avould be a question of habit merely. It 

 may make a species, possibly a new one, rather of Claparede 

 and Lachmann^s genus Plagiophrys. 



As regards the genus Gromia, Duj., to which, to say the 

 least, our Microg. socialis comes most close, Hertwig bases 

 its generic distinctness on the bilateral symmetry of the test, 

 its firmness and inflexibility ; the interspace between the 

 body and the test (though it may at first probably appear 

 but trivial, this is, I fancy, in reality an important cha- 

 racter), the single nucleus. All these are specialities of this 

 form, no doubt ; but whether they are of generic value as 

 distinguished from the genus Gromia is more, I fancy, a 

 matter of opinion than of any real importance — the rhizopod 

 in question, whether we call it Gromia socialis or Microgromia 

 socialis, seems to be, per se, a very distinct thing. Still I 

 have, on a few occasions, met with even a more minute form, 

 undoubtedly a " Microgromia," but not to be, 1 think, iden- 

 tified with my original and Hertwig's form. I venture to 

 call it (at least ad interim) 



Microgromia mucicola, sp. nov. (PI. VIII, fig. 9). 



This I at first found nestling only in the thick mucous 

 matrix of the little alga,which I formerly felt obliged to refer to 

 the genus Dictyosphserium, Nag. (but which is really a Des- 



1 F, E. Schulze, ' Schultze's Archiv fiir Mikrosk. Anatomic,' Bd. XII, 

 p. 119, t. vi, f. 7—13. 



