(x8) 
These being its principal distinctive features, how does the unit 
of living matter appear to the eye? It presents itself as an ex¬ 
tremely minute, translucent, jelly-like mass, visible only by aid of 
the microscope, at times perfectly structureless, more frequently 
containing within it granules of different, sizes, with a dense por¬ 
tion known as the nucleus, and within this, often, a darker spot 
termed the nucleolus. It may have formed for itself a limiting 
membrane or “cell-wall,” as is the rule with vegetable proto¬ 
plasm, or not, as we find in the protoplasm of animals. Such a 
living unit, in spite of its simplicity, is a perfect organism of its 
kind, possessing, although in lowly degree, all the functions of 
life. From a single, simple mass of this kind develops every liv¬ 
ing thing. 
For convenience in study, we divide the living world into two 
great kingdoms—the vegetable and tiie animal, but the border¬ 
line between the two is not clearly defined. When a crea¬ 
ture very low in the scale ot life presents itself, it is sometimes 
impossible to determine whether it be a protozoan or a protophyte 
—the lowliest of animals or of plants. The main difference be¬ 
tween the two kingdoms is that plants take their food directly 
from the inorganic world, while animals, unable to do this, feed 
upon vegetable, or other animal, matter; but this rule does not 
always hold, and hence our difficulty. 
Now, I have said that every living thing has its origin in a sin¬ 
gle unit of protoplasm ; let me trace for you, in a simple way, 
this marvellous process of development, as seen in plants and ani¬ 
mals, taking, for illustration, a lower and a higher representative 
of each kingdom. 
Among the lowest of plants are the bacteria, which are simple 
unicellular organisms, i. e. each individual consisting of but one 
protoplasmic cell.* Many of them are so small that they can 
barely be seen even with the highest powers of the microscope. 
Their mode of reproduction is very simple. In some cases, the 
parent-organism gradually elongates, through increase in the 
quantity of its living-matter, or protoplasm, until its former length 
has been about doubled ; then a gradual constriction of the bacte¬ 
rium is observed to occur at its middle, which increases until the 
Fig-5- 
