THE ELEMENTS OF ORGANIC EVOLUTION. 93 
It never becomes selfish except in its perversion. Its 
perversion is its destruction. And from the simple altru- 
istic beginnings of the conjugation of cells in those 
simple organisms arise with evolution all the complex 
possibilities of love, conjugal, filial, and parental. 
In another way the altruistic tendencies are shown 
in the aggregation of cells. Among animals of one cell 
the ordinary processes of division give rise to a new 
organism for each division. But if the new cells formed 
by such subdivision still remain attached to each other, 
a complex organism is built up. It is thus that the 
single germ cell in the higher animals grows into the 
embryo, and the embryo through the stages of infancy 
and youth into the adult organism. 
The co-operation of the members of the colony of 
cells of which the compound animal is composed makes 
possible all the various forms of organic differentiation. 
A single cell is a unit, complete in itself and inde- 
pendent. All the functions possible to it are united in 
a single structure. With a complex organism the dif- 
ferent cells are gathered into groups to form tissues. 
Out of these tissues different organs are built up, and 
each different organ performs a distinct function. In 
the compound structure of man a multitude of cells are 
joined to perform the work of assimilation, and a host 
of others purify the blood; to another multitude is as- 
signed the task of locomotion. Still others, of finer tex- 
ture, receive impressions of external things and trans- 
mit these impressions into the phenomena of motion. 
Specialization, differentiation, organization, and the ex- 
quisite functions of nerve tissue, are all resultants of the 
altruistic co-operation of cells. As individual men under 
altruistic impulses unite together to form societies and 
states, so are individual cells gathered together to form 
the human body. The conjugation of cells is a method 
