RECENT MEMOIRS ON FRESHWATER RHIZOPODA. 115 



abnormal changes brought about by the gradual evaporation 

 of the water during observation. 



From this it will be seen that this remarkable form offers 

 a peculiar exception to the general character of the Lobose 

 pseudopodia. As well as thin and broad protoplasma-plates 

 occur almost linear, branching and anastomosing processes, 

 pointing to the pseudopodia of the truly " rhizopodous" forms. 



But whilst this is so, I venture to think without myself 

 knowing the form, but judging from the graphic figure, that 

 this is an unmistakeably distinct species from every other, and 

 whilst the resemblances pointed out no doubt are there, 

 there is still no identity of any of the pseudopodia of this form 

 (as depicted) with those of any other freshwater form. 



Notwithstanding the apparently favorable conditions the 

 authors were unable to gain any insight into the structure of 

 the body-mass. 



MONOTHALAMIA RhIZOPODA. 



Microgromia socialis (Arch.), Hertwig = Gromia socialis 

 (Archer) (PI. VIII, fig. 8). 



This minute and interesting Monothalamian has been 

 made the subject of a prolonged study, and of a most valu- 

 able memoir by Dr. Hertwig, too long, indeed, to do more 

 than give a brief epitome of his results. It is long since I 

 myself discovered my great and radical error in taking the 

 great agglomerations or colonies, in which this species some- 

 times occurs in mutual combination, as representing an inde- 

 pendent rhizopod of a different genus, but I do not see that I so 

 greatly erred in referring the form to the genus Gromia ; in 

 fact, as I have mentioned, the tendency of observers in this 

 field seems to me to be to make too many genera, at same 

 time there is probably, as Hertwig considers, sufficient 

 reason in the present instance to justify the step. 



Hertwig points out that the smooth and pellucid test pre- 

 sents a bilateral symmetry owing to the slight diversion to 

 one side of the prominent portion forming the very short 

 necklike oral extremity, so that thus a left and right, a dorsal 

 and a ventral, side may be distinguished, but so slight is this 

 deviation that it might be readily overlooked, as indeed I 

 formerly did. Viewed from an end the test appears circular. 

 When forming a dense and large cluster (my supposed 

 " Cystophrys") the constituent individuals of a group radiate, 

 with the oral end inward and become seen with the rounded 

 posterior end outward, which explains my original error of 

 supposing I had before me a group of closed spherical "cells." 



