M1CROGROMIA SOCIALIS. 131 



minating in a short neck and circular aperture ; plasma 

 bluish, granular; nucleus large, with a single nucleole ; 

 a single contractile vesicle situated near the aperture 

 usually present ; pseudopodia arising from a peduncle, 

 attenuate, branching, anastomosing, often connecting 

 numerous individuals into colonies more or less closely 

 aggregated. Multiplication by longitudinal or trans- 

 verse division of the plasma and also by the liberation 

 of zoospores. 



Diameter 25-35 /*. 



Habitat. Aquatic vegetation. 



ENGLAND. Cumberland (Brown) ; Epping Forest, 

 Essex (Gash). 



IRELAND. Calary, Carrig, and Glenmalure, Wicklow 

 (Archer). 



The peduncle from which the pseudopodia arise is 

 characteristic of all those Gromiina which possess 

 anastomosing pseudopodia; in M. socialis it is often 

 short and may consist of little more than a portion of 

 the plasma projecting from the aperture. Multiplica- 

 tion in this species may take place either by longitu- 

 dinal or by transverse division of the plasma; in the 

 former case the division of the plasma (except the 

 pseudopodia) is completed within the test, the daughter 

 individual emerges in an amoeboid state, secretes a test 

 for itself, and may follow an independent existence or 

 remain attached to the parent either by the anasto- 

 mosing pseudopodia or by helping to form a compact 

 colony. When transverse division of the plasma takes 

 place within the test, as described by Hertwig (1874), 

 the moiety near the fundus of the test becomes a free- 

 swimming flagellated zoospore, the subsequent life- 

 history of which has not been followed out. (See 

 Plate LVI, figs. 1-6.) 



The Cystophrys haecJceliana of Archer (1869) proved 

 to be merely the closely-aggregated colonial form of 

 M. socialis. When it occurs in a solitary form the 

 pseudopodia are of a filose character ; when the indi- 



