THE LIFE OF THE SLIGHTLY COMPLEX ANIMALS 95 
there is formed a group of a few or many cells, each cell 
having the structure of the simpler unicellular forms. 
These cells are held together in a gelatinous envelope, and 
the mass is usually spherical in shape. In most of the 
colonies each of the cells possesses two or three long, pro- 
toplasmic, whiplash-like hairs, called flagella, and by the 
lashing of these flagella in the water the whole group swims 
about. 
14. Gonium.—If, when one of the simplest animals di- 
vided to form two daughter cells, these two cells did not 
move apart, but remained 
side by side and each di- 
vided to form two more, 
and each of these divided 
to form two more, and 
these eight divided each 
into two, each cell com- 
plete and independent but 
all remaining together 
in a group—if this pro- 
cess should take place we 
should have produced a 
group or colony of sixteen 
cells, each cell a complete 
animal capable of living 
independently like the 
other simplest animals, 
but all holding together 
to form a tiny, flat, plate- Fre. 12—Gonium pectorale (after STEIN). A, 
like colony. Now, this is ee ai above; B, colony seen 
precisely what takes place 
in the case of those colonial Protozoa belonging to the genus 
Goniwum (Fig. 12). When the mother cell of Goniwm. di- 
vides, the daughter cells do not swim apart, but remain 
side by side, and by repeated fission, until there are sixteen 
cells side by side, the colony.is formed. Each cell of the 
