2 THE ORIGIN OF PLANT AND ANIMAL CHILDREN 
plants and animals. The word “ animal ” includes all 
species, from the microscopic forms which live in the water 
to the highest and most 
complex, man. The 
number of such cells in 
one person is almost be¬ 
yond imagination. In 
one joint of the finger 
there are perhaps , 
100,000,000, possibly 
twice that number. Yet 
all the cells of various 
kinds and unimaginable 
number, composing the 
body of any plant or 
animal, came into exist¬ 
ence by a process of growth from the protoplasm of a single 
cell. The methods of that process are the first things we 
shall study. 
1. Of what is a cell composed? 
2. What is tissue ? 
3. What is the origin of the millions of cells which compose a 
body? 
Cell Division. — In the tiny plants and animals composed 
of single cells, and also in many living forms composed of a 
multitude of cells, there is 
a very simple method of 
reproduction called asex¬ 
ual (a means not ). In the 
scum which forms at the 
surface of a dish of water 
in which something is de¬ 
caying, great numbers of 
one-celled animals may be 
seen with a microscope. 
The three stages represent the process of 
division in a one-celled animal. 
Figure 1 . — A Diagram of Tissue. 
Within each large cell of the tissue is a 
nucleus, and within the nucleus a nucleolus 
(little nucleus). The cells rest upon a net¬ 
work of fibers, between which are the small 
cells which produce and care for them. 
