PI. VII. — I, Vinelike colony of the bryozoan, Plumatella, on 

 the underside of a stone ; the heads are white and the homy 

 tubes very dark. 2, Half inch of stone surface covered with 

 the protozoan Vorticella; the blurred white spots are the 

 moving animals p. 57. 



Photo, by A. H. Morgan 



