Gonium pectorale colonial algae. Light microscopy footage of colonies of the green alga Gonium pectorale. Colonies of this alga may comprise 4 to 16 cells arranged in a flat plane and bound together by a gelatinous extracellular matrix or by gelatinous strands. Each cell has two rotating flagella which cause the colony to tumble in their motion. They contain one chloroplast and a red pigmented primitive eye-spot.