microscope teaches us that the tissues of animals and plants are built upon kindred lines.  We meet with cells and fibers in both.  The cell is in each case the primitive expression of the whole organism.  Beyond cells and fibers we see the wonderful living substance, protoplasm, which is alike to our senses in the two kingdoms, although, indeed, differing much here and there in the results of its work.  On purely microscopic grounds, we cannot separate animals from plants.  There is no justification for rigidly assuming that this is a plant or that an animal on account of anything the microscope can disclose.  A still more important point in connection with this protoplasm question consists in the fact that as we go backward to the beginnings of life, both in animals and plants, we seem to approach nearer and nearer to an identity of substance which baffles the microscope with all its powers of discernment.  Every animal and every plant begins existence as a mere speck of this living jelly.  The germ of each is a protoplasm particle, which, whatever traces of structure it may exhibit, is practically unrecognizable as being definitely animal or plant in respect of its nature.  Later on, as we know, the egg or germ shows traces of structure in the case of the higher animals and plants; while even lowly forms of life exhibit more or less characteristic phases when they reach their adult stage.  But, of life’s beginnings, the microscope is as futile as a kind scientific touchstone for distinguishing animals from plants as is power of movement, or shape, or form.

A fourth point of appeal in the matter is found within the domain of the chemist.  Chemistry, with its subtile powers of analysis, with its many-sided possibilities of discovering the composition of things, and with its ability to analyze for us even the light of the far distant stars, only complicates the difficulties of the biologist.  For, while of old it was assumed that a particular element, nitrogen, was peculiar to animals, and that carbon was an element peculiar to plants, we now know that both elements are found in animals, just as both occur in plants.  The chemistry of living things, moreover, when it did grow to become a staple part of science, revealed other and greater anomalies than these.  It showed that certain substances which were supposed to be peculiar to plants, and to be made and manufactured by them alone, were also found in animals.  Chlorophyl is the green coloring matter of plants, and is, of course, a typical product of the vegetable world; yet it is made by such animals as the hydra of the brooks and ponds, and by many animalcules and some worms.  Starch is surely a typical plant product, yet it is undoubtedly manufactured, or at least stored up, by animals—­a work illustrated by the liver of man himself, which occasionally produces sugar out of its starch.