194 TEE SCIENTIFIC MONTHLY
oompnlfiory and voluntary, yet developed on the earth. The production of conspicuous flowers, of nectar and other devices for the perpetuation of species of plants is a form of compulsory service originating mostly during the Cenozic, though undoubtedly some of these devices received their inception in the Mesozoic.
The development in the Cenozoic of the living groups of birds was accompanied, if it did not originate in the Mesozoic, with the hatching instinct. A considerable amount of this instinct is, however, voluntary service, since it differs bo greatly among individuals of the same spe- cies or variety. After the young are hatched the parents are doubtless compelled by instinct to feed and protect them, but here again much of the service is without doubt voluntary. (Since the birds of the Mesozoic were reptile-like in the sharp teeth, daws upon the wings and long vertebrated tail possessed by most individuals, they may also have been reptile-like in their failure to personally hatch their eggs and feed and protect the young.)
The appearance of carnivore, rodent and hoofed mammals in the lower part of the Cenozoic initiated a much higher type of voluntary service. These mammals, to judge by their nearest living relatives, were compelled to serve their young before birth by interuterine nouridi- ment and after birth through the secretion of milk. They also pro- tected their young as well as their mates, and procured them solid food. They were doubtless impelled to these latter acts by instinct, but a con- siderable amount of voluntary service was present.
In the upper part of the Cenozoic appeared man, and with him b^an the development of the highest type of voluntary service yet evolved upon this earth. Slowly, extremely slowly, it advanced at first and was for long doubtless limited to the family; gradually, however, it was ex- tended to other members of the clan, nation, language and finally even to the barbarian, heathen or gentile, and even to lower animals and to plants. Man is, however, still under the law of compulsory service. The imbom young must still be given interuterine nourishment and the young child food and care, while public opinion and man-made laws force the laggard to duties which he is not yet sufficiently evolved to perform voluntarily.
We thus see that the development of life upon this earth was due to mutual service, that without such service no higher forms of life could have evolved. Animals can live only through the death of other animals or of plants. Both animals and plants are compelled to give of their strength, or often of life itself, in the production of young. As animals and plants became more highly evolved they developed a higher type of service, that of furnishing more nourishment and better protection to their offspring. Very gradually, side by side with the higher kinds of
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