INSECTS
The environmental conditions of the life of cells in a complex animal are too complicated for an elemental study; the elements of life and its basic necessities are better understood in a simple organism, or in a one-celled animal; but for purposes of description, it is most convenient to speak of the properties of mere protoplasm. All the vital needs of the most highly organized animal are present in any part of the protoplasmic substance of which it is composed.
Fig. 62. Diagram showing the relation of the germ cells (GCls) and the body cells (BCls) in successive generations
A fertilized germ cell of generation A forms the germ cells and body cells of B, a fertilized germ cell of B forms the germ cells and body cells of C, and so on. The offspring C of B derives nothing from the body cells of the parent B, but both offspring C and parent B have a common origin in a germ cell of A
Protoplasm is a chemical substance, or group of substances, the structure of which is very comp]ex but is maintained so long as there is no disturbance in the environment. Let some least thing happen, however, such as a change in the temperature, in the strength of the light, in the weight of pressure, or in the chemical composition of the surrounding medium, and the protoplasmic molecules, in the presence of oxygen, are likely to have the balance of their constituent particles upset, whereupon they partly decompose by the union of their less stable elements with oxygen to form simpler and more permanent compounds. The decomposition of the protoplasmic substances, like all processes of decomposition, liberates a certain amount of energy that had been stored in the making of the molecule, and this energy may manifest itself in various ways. If it
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