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ment of her ovaries, so that she may begin to lay eggs very soon after emergence. This is also indicated by the conditions in the Meliponinæ. The Melipona queen, which is reared in a closed cell of the same size as that of the workers and on the same amount of food, emerges with rudimentary ovaries and has to develop them by subsequent feeding during her adult instar, whereas the Trigona queen, which is reared in a large cell with more food than is given to the worker larvæ, emerges with mature or nearly mature eggs in her ovaries. All these queens, however, are distinguished from the cospecific workers by certain degenerate or primitive characters, which, it would seem, must owe their peculiarities either to the indirect, inhibiting or modifying action of chemical substances (enzymes) in their food or to the more direct action of hormones, or internal secretions produced by the developing ovaries. The great size of the ovaries in the queens of all these social bees accounts, of course, for their extraordinary fecundity and the size of their colonies. Cheshire computed the number of eggs which may be laid during her lifetime by a vigorous, fecundated honey-bee queen as about 1,500,000, and, according to von Buttel-Reepen, we should find in her spermatheca no less than 200,000,000 spermatozoa. It is not surprisisng, therefore, that a hive, at the time of its climax development during the early summer, may contain 50,000 to 60,000 or even 70,000 to 80,000 bees.

In conclusion I may refer to one of the negative peculiarities of social bees the absence of that peculiar interchange of nutriment between the adult and larva, or trophalaxis, which seems to be a powerful factor in integrating and maintaining the colonies. of the social wasps. Among the Meliponinæ the food and egg are simply sealed up in the cell, so that there can be no contact between adults and larva, and even the honey-bee worker does not place the food on the mouth of the larva but pours it on the bottom of the cell where it can be imbibed when needed. So far as known, the bee larva, unlike the wasp larva, produces no salivary secretion to attract its nurses, though it might be going too far at the present time to say that this is certainly not the case. It is quite probable, nevertheless, that the sources of the development and perpetuation of adult and larval contact, so essential to the maintenance of social life among the Bombinæ, Meliponine and Apinæ, are to be looked for in other directions. Hermann Müller long ago pointed out, as I stated in the preceding lecture, that the transition of the adult wasp from an insect to a nectar and pollen diet was due to economy of food. These latter substances represent a very concentrated and energizing food supply and one that can be

more readily obtained in great abundance than insect food. Hence it is not surprising that a large group of insects like the bees has become so exquisitely anthophilous, and that the exploiting of larval secretions is unnecessary. It will be noticed that all three subfamilies of social bees store quantities of pollen and honey in open cells and such easily accessible stores of liquid and very finely divided food make even the reciprocal feeding of the adult workers in bee colonies superfluous. This storage of food may be at least one of the reasons why such exchanges of nutriment as we observed among the social wasps and shall see again in a more exaggerated form among the ants and termites were either never developed or were long ago discontinued by the social bees.

Vol. XV.-22.

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able, but this fourth-a complete break with "modern civilization"-does not seem at all probable. These three courses are: (1) that the whole human race be involved in the rapidly growing whirlwind which in its present stage of development we call, rather proudly "our civilization" as though we had deliberately planned it as a complete entity, when no one ever conceived of such a thing, and no one even to-day has the ability properly to evaluate the civilization now in existence; (2) that a part of the human species, reluctant to mutate or evolve into the strange new species which the onward sweep of "civilization" is producing, deliberately keep themselves apart in the yet remaining open places, guarding these zealously as the domain of the creature known to-day by scientists as Homo sapiens, the remainder of the race evolving rapidly into some other kind of Homo, or even into a different genus in time; (3) that the entire race of Homo, not wishing to become anything other than sapiens, but rather more so, and making use of all his splendid new means of intercommunication the world around, construct an intelligent plan to conserve all the best that the wilderness contained and preserve these perpetually in close conjunction with the best, and only the best, which innovations have to offer.

The wilderness and the path, so easily at odds to-day, must be restored to harmony, a harmony built upon a foundation which cannot again be shaken. The best of all that earth and heaven can yield is none too good for lordly man as he aspires to a better, greater man in future.

Many questions will arise in evaluating the permanent worth of the host of innovations daily pressing their almost irresistible claims upon us. But we will not willingly let the spirit of the machine grind us in its cogs until we are ourselves converted into mere machines of clay, reflecting the nature of the machine-civilization -which ground us.

The great machine civilization, embracing all its component machines and inventions and discoveries and methods of life, would then need to be kept thoroughly human, humanized by all the best that is in the human heart, with all the love of the beautiful, with all the esthetic joy in wild and lovely scenery, with all the satisfying health from breathing air of wilderness purity, with all the thrill of action when the muscles and sinews of the man propel him exultantly through the forest, over the mountains and through the waters. No mere combination of automobile and cloud of dust and office chair can truly satisfy the Homo sapiens of the ages. The path must lead quickly to the wilderness. The wilderness must even pervade and beautify the aggregations of our paths. The bare, artificial ugliness of the modern city must be stripped

THE PATH AS A FACTOR IN HUMAN
EVOLUTION

By RALPH E. DANFORTH

UNIVERSITY OF PORTO RICO

HE path and the wilderness, formerly in harmony, are now at odds. Certain elements of the wilderness are essential to the best evolution of man. The path is also essential; therefore a reasonable measure of harmony between it and the wilderness should be restored and retained. This restoration and retention might be included in our broad term conservation.

Millions of years before man became human some of the primitive worms and insects made paths; some of the lower vertebrates did likewise, and many of the earliest mammals of remote Triassic times doubtless made paths and runways of many sorts. Triassic, Jurassic and Cretaceous together constitute the Mesozoic, or age of reptiles, which according to some geologists lasted nine million years; and throughout this long time our earliest mammalian ancestors were small creatures, the largest not exceeding a rat or rabbit in size, hiding for their lives from many a reptilian foe, both large and small.

With the close of the age of reptiles and dawn of the age of mammals, which some estimate to have been three million years ago, mammalian species evolved with great rapidity and in many directions. Mammals small, medium and large, and of wonderful diversity were produced. Of these some still made paths of one sort or another, and many of their constantly evolving offspring continued to do likewise.

Among our modern mammals we now find many famous pathmakers. When man's more recent ancestors departed from arboreal life and remained more upon the ground again, like their remoter pre-arboreal ancestors, they must have made frequent use of the ready-made paths of their contemporaries, some of which fell victims to early man, while others at times made of him a victim. From that time, throughout the many thousands of years of savagery man made an increasing use of paths, himself becoming an important pathmaker where he walked from place to place repeatedly, yet often departing from his paths to search the all-surrounding wilderness.

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