capable of evolution. The organ, that much is certain, develops—that is, it passes through a series of transformations before assuming its final form. Any part of every organism will furnish the proof. But what determines the final form during phylogenetic evolution? I answer, Function. With its assertion begins the differentiation of the substratum of primitive beings. It is not the organ from which function derives its origin, but just the reverse. The functions create their organs, or, to use a better definition, necessity determines the organic form, which hence becomes hereditary, and ultimately in the embryo of the higher animals in structure at least precedes function.
When the embryo of the land-salamander, many months previous to the normal time of its entry into the world, is taken out of the egg and kept in water well supplied with oxygen, neither too warm nor too cold, nor too dark, and amply fed with small living water-animals, and if care is taken that the creature can not get out of the water, its organism will change. It has to inhale the oxygen dissolved in the water, not that of the atmosphere, like its parents breathing with lungs. Its lungs therefore remain undeveloped, but by way of compensation strong gills appear at each side of the head. The originally very feeble function of respiration through gills, in conformity with the increased demands of the growing body, creates a new organ, or calls forth one possessed by its remote ancestors. The animal, moreover, feels the necessity to swim, not to creep, like its terrestrial parents. Its four extremities, therefore, become mere rudimentary appendages, while, on the other hand, a vigorous rudder-tail develops. The function of swimming calls forth fins, new organs which the parents lack. Thus a substantially new animal is produced, which elsewhere does not exist, and which shows how through the development of new functions new organs are formed, or, as it were, resuscitated.
This principle applies not only to particular cases with artificially created conditions but to all functions. All of them precede the organs devoted to their exclusive service. All of them originate through competition for the necessaries of life. At first a simple want is easily satisfied by simple means, but gradually the organism is called upon to meet numerous demands requiring complex contrivances through differentiation.
Instruments, apparatus, engines, are tools or organs invented by human beings, because the wants of better food, better air, better water, or the necessity of saving space and time, or of having means of communication, protection etc., become more and more pressing among them. They have, as it were, become part of the organism. Such newly invented artificial organs as the spectacles, the watch, the shoe, have all a long history of evolution.
The kitchen, with all its large and small utensils for the cooking and mixing and chemical preparation of the raw produce of the animal and vegetable kingdoms, may be looked upon as one single digestive
