MICROGROMIA SOCIALIS. 131 



minating in a short neck and circular aperture ; plasma 

 bluisli, 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 25-36 ju,. 



Habitat. — Aquatic vegetation. 



England. — Cumberland {Brown) ; Bpping Forest, 

 Essex (Cash). 



Ireland. — Calary, Carrig, and Glenmalure, Wicklow 

 (Archer). 



The peduncle from which the pseudopodia arise is 

 characteristic of all those G-romiina 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 Gystophrys haeckeliana 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- 



