FLAGELLATED PROTOZOA 



59 



limited to a certain number of cells, and this number always 

 reappears upon reproduction so that the multicellular individual 

 is much more specific in nature, as in Gonium pectorale where 

 the individual always consists of 16 cells (Fig. 25). 



These colony forms are of peculiar interest in that they have 

 many features in common with the higher animals and plants, 



FIG. 25. Gonium pectorale, a colony of flagellated protozoa consisting of sixteen 

 cells arranged in a flat plate, three on a side and four in the center. Each cell 

 carries two flagella. Photograph from a preparation. 



but the cells are not differentiated for the performance of differ- 

 ent functions, each one acting for itself rather than for the ag- 

 gregate as a w r hole. They represent, therefore, a phase in 

 complexity of form and function intermediate between the uni- 

 cellular organisms (protozoa, protophyta) and the multicellular 

 (metazoa and metaphyta). 



