We began with the amoeba. This could not have been the beginning.
In all its structure it tells us of something earlier and far
simpler, but what this earlier ancestor was we do not know. Rather
more highly organized relatives of the amoeba, the flagellata,
have produced a membrane, and swim by means of vibratile,
whiplash-like flagella. We must emphasize that these little animals
correspond in all essential respects to the cells of our bodies;
they are unicellular animals. And the cell once developed remains
essentially the same structure, modified only in details, throughout
higher animals. And these unicellular animals have the rudiments of
all our functions. Their protoplasm and functions seem to differ
from those of higher animals only in degree, not in kind. And the
more we consider both these facts the more remarkable and suggestive
do they become.
Cells with membranes can unite in colonies capable of division of
labor and differentiation. And magosphaera is just such a little
spheroidal colony. But the cells are still all alike, each one
performs all functions equally well. But in volvox division of labor
and differentiation of structure have taken place. Certain cells
have become purely reproductive, while the rest gather nutriment for
these, but are at the same time sensitive and locomotive, excretory
and respiratory.
Pages:
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143