OBSERVATIONS ON POLTZOA. 219 



Locality, Georgetown, Mass. 



Remarks. The ccenoecia cover large areas, differing in 

 this respect from all the other Fredericellse, whose colo- 

 nies when upon a flat surface are never very diffuse. 



The more open growth, or variety a, was found in a 

 shallower and more rapid part of the stream than variety 

 6. Their peculiarities fit them for these different situa- 

 tions. Variety a exposes only its single cell to the 

 action of the swift current, the remainder being firmly 

 fastened, while variety b, not being in danger from the 

 current, indulges in a freer and more dendritic growth. 



I have taken the liberty of dedicating this species to 

 Miss Elizabeth Walcott, of Salem, in whose agreeable 

 society I had the pleasure of discovering it, during a 

 field meeting of the Essex Institute. 



FREDERICELLA PULCHERRIMA Hyatt. 



Ccenoecia radiating more distinctly than in any other 

 species, resembling in this respect Plumatella. Branches 

 colorless, generally attached throughout ; the free portions 

 of the cells occasionally subdividing into free branches. 

 Polypides do not differ sensibly from those of Fredericella 

 regina. Statoblasts measure about .5 m. m. long, by 

 about .16 m. m. broad (PI. 15, fig. 3). 



Remarks. The only locality is White's Bridge, at the 

 outlet of Lake Sebago, Maine. The colonies upon the 

 bark of branches near the shore were young, and had not 

 yet attained their growth, but it is probable that the 

 adults upon such surfaces are never so symmetrical as 

 those upon the stems of the water-lilies. 



FREDERICELLA REGINA Leidy, Mss. 



The ccenoecia are scarcely describable in general terms, 

 since they display almost all kinds of growth ; but there 

 are three principal varieties. 



Variety a, PI. 7, fig. 1. The colonies are not very 

 large, but the branches are numerous. The attached 

 parts of the cells are very long, but the free portions mere 



