TRE AND THE OUTFLOWING
NETWORK OF LIVING MATTER, ALONG WHICH GRANULES ARE CONTINUALLY
TRAVELLING, AND BY WHICH FOOD PARTICLES ARE ENTANGLED AND DRAWN IN

_Reproduced by permission of the Natural History Museum_ (_after Max
Schultze_).]

As the result of much more explosive life, animals have to deal with
much in the way of nitrogenous waste products, the ashes of the living
fire, but these are usually got rid of very effectively, e.g. in the
kidney filters, and do not clog the system by being deposited as
crystals and the like, as happens in plants. Sluggish animals like
sea-squirts which have no kidneys are exceptions that prove the rule,
and it need hardly be said that the statements that have been made in
regard to the contrasts between plants and animals are general
statements. There is often a good deal of the plant about the animal, as
in sedentary sponges, zoophytes, corals, and sea-squirts, and there is
often a little of the animal about the plant, as we see in the movements
of all shoots and roots and leaves, and occasionally in the parts of the
flower. But the important fact is that on the early forking of the
genealogical tree, i.e. the divergence of plants and animals, there
depended and depends all the higher life of the animal kingdom, not to
speak of mankind. The continuance of civilisation, the upkeep of the
human and animal population of the globe, and even the supply of oxygen
to the air we breathe, depend on the silent laboratories of the green
leaves, which are able with the help of the sunlight to use carbonic
acid, water, and salts to build up the bread of life.

Sec. 2

The Beginnings of Land Plants

It is highly probable that for long ages the waters covered the earth,
and that all the primeval vegetation consisted of simple Flagellates in
the universal Open Sea. But contraction of the earth's crust brought
about elevations and depressions of the sea-floor, and in places the
solid substratum was brought near enough the surface to allow the
floating plants to begin to settle down without getting out of the
light. This is how Professor Church pictures the beginning of a fixed
vegetation--a very momentous step in evolution. It was perhaps among
this early vegetation that animals had their first successes. As the
floor of the sea in these shallow areas was raised higher and higher
there was a beginning of dry land. The sedentary plants already spoken
of were the ancestors of the shore seaweed