26 ANIMAL LIFE 
colony eats and breathes and feels for itself; each can and 
does perform all the processes necessary to keep it alive. 
When ready to multiply, the sixteen cells of the Gonium 
colony separate, and each cell becomes the ancestor of a 
new colony. 
15. Pandorina.— Another colony usually composed of six- 
teen cells is Pandorina, but the cells are arranged to form 
a spherical instead of a plate-like colony (Fig. 13). In Pan- 
dorina morum the colony consists of sixteen ovoid cells in 
a spherical jelly-like mass. Each cell has two flagella, and 
by the lashing of all the flagella the whole colony moves 
through the water. Food is taken by any of the cells, is 
assimilated, and the cells increase in size. When Pan- 
dorina is ready to multiply, each cell divides repeatedly 
until it has formed sixteen daughter cells. The inclosing 
gelatinous mass which holds the colony together dissolves, 
and the daughter colonies be- 
come free and swim apart. 
Each colony soon grows to the 
size of the original colony. 
This kind of multiplication or 
reproduction may be continued 
for several generations. But 
it does not go on indefinitely. 
After a number of these gener- 
ations has been produced by 
simple division, the cells of a 
colony divide each into eight 
Fie. 13.—Pandorina sp. (from Na- instead of sixteen daughter 
ture). ‘The cells composing the cells. The daughter cells are 
form Wanghter colonies, Ob all of the same size, but 
the difference is hardly notice- 
able. The eight cells resulting from the repeated division 
of one of the original cells separate and swim about inde- 
pendently by means of their flagella. If one of these cells 
comes near a similar free-swimming cell from another 
