17 
LIFE: ITS ORIGIN AND NATURE 
vert them into the living plant. Animals do 
not and cannot subsist directly upon inorganic 
substances. They must derive them indirectly 
either through plants or the tissues of other 
animals, which in turn have fed upon plants. 
In this way, inorganic substances are supplied 
to the body, but animals cannot directly appro¬ 
priate inorganic substances of any kind. Plants 
do so, and we seem to have here a case in 
which inorganic matter is converted into living 
substance, and in a certain sense, therefore, life 
produced from not-life. There is, however, 
this point: that the vegetable or plant merely 
feeds in this manner, and is in no way origin¬ 
ally generated by the food of which it partakes. 
The plant originated from another plant, so 
that the laws of heredity apply to it directly, 
as before pointed out, and it is not, strictly 
speaking, an example of spontaneous genera¬ 
tion at all. 
The life of any individual only begins, of 
course, in the union of the sexual elements 
derived from the parents, and the above dis¬ 
cussion has been limited to the ultimate origin 
of life upon our planet. Further, it is now 
known that many unicellular organisms do not 
multifly by sexual conjugation at all. They 
multiply by “fission,” a mother-cell splits into 
two daughter cells, which, when they have 
grown to the normal size, again divide,—and 
so on forever. There is never any normal 
death among these lower orders of being, and 
there has never been any sexual conjugation to 
initiate them. The problem therefore remains 
as to their origin, together with the problem of 
