1-h ■^.06 (73) Ha hVOUiTLOS 1927-38 4i h FOR THE PEOPLE FOK EDVCATION FOR SCIENCE LIBRARY OF THE AMERICAN MUSEUM OF NATURAL HISTORY DsoNigiiinw b'.Ofe(YV^rc^ Vol. III. No. 4 MAY, 1932 20 Cents EUOLUnON A JOVRTSAL OF NATURE WHAT MADE THE FLOWERS? Keystone-UndeTwood Photo (See Page 3) Page two EVOLUTION May, 1932 Scientific Advisory Board Anton J. Carlson Henry E. Crampton Martin Dewey Wm. King Gregory Paul B. Mann Elihu Thomson Managing Editor L. E. Katterfeld EUOLUTiON A Journal of Nature For popular education in natural science to combat bigotry and superstition and develop the open mind Science Editor Allan Broms Contributing Editors Edwin Tenney Brewster Pauline H. Dedereh Carroll Lane Fenton Maynard Shipley Henshaw Ward Horace Elmer Wood II. YOU will note two additions to Evolution's editorial staff. Prof. A. J. Carlson, Head of Physiology Depart- ment of Chicago University, joins our Scientific Advisory Board. Dr. Henshaw Ward, author of "Evolution for John Doe" and "Charles Darwin: The Man and his Warfare," becomes one of our Contributing Editors. Readers who know Professor Carlson and Dr. Ward will already appreciate our good fortune in securing their active co-operation. TN RESUMING publication of Evolution we wish first to express our appreciation for the support of the manv friends of science freedom whose contributions have made this possible. We shall strive to prove that their confidence was merited. We hope not only to bring Evolution out reg- ularly, but to make it a still better instrument for arousing a more general interest in natural science, and a more effec- tive champion of science teaching against the forces of or- ganized superstition. T7VEN if the fundamentalists made no fuss at all there ■'"^ would be need and a field for a natural science journal that is "easy to read" and always accurate. More research work is being done now and more exploration parties are in the field than ever before, and Evolution will help to pass their newly-found information along. There is too great a spread between what the scientific world accepts and knows, and what the mass of the people understand. Evolution will help to bridge this gap. We hope also that teachers and scientists, busy with their specialties, will find Evolution useful for its reliable information outside their own fields. BUT fundamentlism is neither dead nor asleep. Funda- mentalist magazines are constantly agitating their readers regarding the "dangers" of evolution, assuring them that "real" scientists are discarding the "theory", and preparing them for the promised campaign to outlaw evolution teaching through popular referendum vote. This influence has tre- mendous effect at present through teaching in the schools. And in thousands of school administrations, as for instance in Boston, medievalism is in the saddle and prevents the High School biology teachers from dealing with evolution at all. ' I 'HE only solution for this problem is general popular -^ education in natural science. When a sufficient number of people have some inkling of what is meant by a scientific approach to a question instead of accepting opinions dogma- tically handed down by authority, this situation will change. There is literally no way to measure the far-reaching effect that a general recognition of man's place in nature, as indi- cated by the fact of evolution, would have upon the endeavors of the human race. It is a matter of surpassing importance. OVEN in these days of depression the work of popular education must go on. It is needed all the more. So, now that Evolution has started again, we urge every one of our old readers, as well as the hundreds of new ones that jtart with this issue, to become active supporters of this great work. The most immediate task is to double the present paid circulation of Evolution, so as to make the journal self-sustaining. Please do not keep this copy to yourself, but show it to your friends and secure a little club of new Evolu- tion subscribers. And, if possible, also contribute a check to be used in Evolution's educational campaign. NEW EVIDENCE FOR EVOLUTION Perhaps the most impressive evidence for evolution is the fact that so many different lines of evidence from entirely independent fields of investigation all point to the same con- clusion. If there was only one chain of evidence, then a "missing link" might be of some importance. But this loses its significance entirely in view of the multiplicity of inde- pendent proofs. In this issue we present evidence from a comparatively new field of research, about which Darwin and Huxley knew practically nothing. And yet everything that is being dis- covered today supports the view of these old masters, that evolution is a fact. We refer to the evidence from Parasito- logy in the article by Professor Robert Hegner. In our next issue the article by Professor H. Gideon Wells will bring more new evidence from Biochemistry. Although for some of our readers it may prove rather difficult to master this mater- ial, we are sure they will find it eminently worth while. And perhaps it will also prove entertaining to bring this new evi- dence for evolution to the attention of fundamentalist friends. SCIENCE CONGRESSES Three Science gatherings this summer will interest readers of Evolution. American Association for the Advancement of Science at Syracuse, N. Y., June 20-25. Particulars from Permanent Sec'y A.A.A.S., Smithsonian Institution, Washington, D. C. International Eugenics Congress at American Museum of Natural History, N.Y.C., August 22-24. Address: Third In- ternational Congress of Eugenics, Cold Spring Harbor, N. Y. International Congress of Genetics at Ithaca, N.Y., Au- gust 24-3 L Information from C. C. Little, Sec'y. Jackson Memorial Laboratory, Bar Harbor, Maine. EVOLUTION, May, 1932, Vol. Ill, No. 4 (Whole No. 19) Published monchlv by EVOLUTION PUBLISHING CORPORATION, 200 Varick St.. New York, Editorial Address: Route 4, Hempstead, N. Y. Application for Second Class Entry pending at Post Office, New York, N. Y. Single subscription $2.00 a year; additional subscriptions $1.00 each; Foreign, 10c extra; Single copy, 20c; bundles of 12 or more, 8 l/3c per copy. May, 1932 EVOLUTION Page What Made the Flowers? By HENSHAW WARD TF ANYONE asks what made the leaves of plants, he is proposing a question that has no answer, for no one can tell how leaves happened to come into existence. But botanists know that "What made the flowers?" is one of the most pregnant queries ever put by a naturalist, and that the answer is the prettiest one in the domain of evolution. Insects made the flowers. Before this answer can be understood, we must know what a flower is. It is an apparatus by which plants make seeds. There is a bewildering variety of flowers, working in various ways; but the most common kind, the kind with which this article deals, consists of two organs. One of these, called a stamen, produces the male element that goes to the making of an embryo. At the top of the stalk of a stamen is a knob in which are fine grains of pollen. These grains correspond to the male element, the sperms, in animals. The second organ, called a pistil, produces the female element that goes to the making of an embryo. At the base of its stalk is an ovary which contains eggs that are waiting to be fertilized. Botany for Colleges — Ganong: Macntillan In flower at left, Salvia pratensis, hinged lever arrangement brings stamens down on body of bee. Moth in Yucca flower at right, carries pollen from another flower, tamps it down and lays egg in it. If you look closely at a typical flower — say a wild rose — you will see at the base of the colored petals a circle of several dozen stamens, each of which is a little stalk that bears aloft its pollen-sac. Within this' circle of stamens is a cluster of pistils; each of them is rough and sticky on the upper end of its stalk, and each one terminates below in an egg-sac. The business of every stamen is to convey its pollen to the top of some pistil; the purpose of every pistil is to capture a pollen- grain that will fertilize its egg. Unless the egg is fertilized by pollen, it is barren and cannot produce a seed. This process of fertilizing is called "pollination." And the need of pollination is the origin of all the colored flowers. If you think of an ear of corn, you can realize what pol lination means. On the cob of the young ear were clustered a dozen rows of pistils waiting to be fertilized. From each pistil extended a long, delicate thread, which reached to the end of the cob and stretched out into the air. We call this set of pistils the "silk" of the ear. Two feet above the ear. at the top of the cornstalk, was a cluster of stamens, which we call the "tassel." When mating-time comes for the plant, the pollen-sacs of the tassel open and spill their contents. The microscopical grains float down through the air. When one of them lights on the tip of a thread of silk, it is straightway transformed into a thing of life. It sends out a most slender and delicate tube, so small that it can force a passage down through the core of the silk thread, dissolving, really eating, its way along the whole length until it reaches the egg. There its nucleus combines with the nucleus of the waiting egg. And what then? At that moment the embryo of a new kernel of corn is created. This grows as the weeks pass until it be- comes one of the hundreds of juicy kernels that are set on the surface of the cob. If it is not gobbled by hungry animals, but is allowed to grow hard, is kept through the winter, and put under ground next spring, it will sprout and grow into a new cornstalk. Thus we see that a corn plant is complete within itself: its ovaries are fertilized by its own pollen. If one cornstalk stood all alone in the midst of a large space, it could be self- sufEcient with its own pistils and stamens. Yet in an ordinary cornfield, on a windy day when the tassels are ripe, the air is full of pollen, and many silky pistils are fertilized by pollen that is blown from another plant. Such pollination is called "cross-fertilization." Some plants cannot be fertilized by their own pollen; and experiment has shown that most plants are more surely and richly fertilized by the pollen from another plant. The general rule of nature is that most plants re- quire, or are better off with, cross-fertilization. Grasses and trees send out in the spring vast numbers of pollen-grains, which fill the air in uncounted millions. The pine, for ex- ample, commits to the breezes a kind of pollen-grain that is wafted by means of air-sacs on either side of it. Perhaps only one in a million finds a pistil. It is a fearfully extravagant method, but it succeeds. It accomplishes the cross-fertilization that plants are in need of. Plants with conspicuous flowers are not so extravagant. They have found a cleverer way of conveying pollen. They lure and bribe insects to do the carrying. Watch this bee that is buzzing up to a head of clover. She has been attracted by the bright red spot in the landscape, for she knows that it advertises food. She likes the odor, because it certifies to the presence of food. She confidently runs her tongue into the bell of one of the flowerets, and finds, sure enough, a sip of the nectar that she can convert into honey. That is all she thinks of — nectar. But the flower has quite other thoughts. It quickly sticks some pollen-grains on to the bee's head. The bee flies to another flower. As she presses eagerly forward for the next drop of nectar, some of the pollen-grains that she has been transporting are rubbed off and gathered in bv the rough, sticky tops of the greedy pistils. The bee has. all unconsciously, accomplished cross-fertilization for the clover. If botanists knew only of the ways in which insects carry pollen for clover and roses and buttercups and lilies, they would never suppose that they knew the answer to "What made the flowers?" They might guess that these four flowers had developed, through a long course of evolution, such showy and sweet-scented mechanisms as were adjusted to the taste of insects, that the blossoms had been gradually shaped by the success of those plants that varied in such ways as to grow more and more attractive to insects. It might be a likely guess that insects, by avoiding the less pleasant flowers and Page four EVOLUTION May, 1932 visiting the more pleasant ones, had actually shaped and colored and given odors to the blossoms that catered to their preferences. But this would be only a guess. Until many naturalists had studied thousands of species of plants for almost a century, they were not well-enough informed to establish a reliable theory of how the insects made the flowers. But sixty years ago they had acquired so much knowledge of the relations of plants to insects that they felt pretty confident of the theory — which Darwin first elaborated. Since then all added knowledge of botany confirms Darwin's theory, and no knowledge has run counter to it. Today every botanist as- sumes that flowers were developed, in the course of millions of years', by the adaptations that plants made for inviting and employing and rewarding the insects. In this brief article we can look at only a few examples of those thousands of devices which have been evolved by plants in their efforts to use insects as pollen-carriers. A series of five facts should be clear in a reader's mind if he is to realize the meaning of the devices. (1) The sweet juice of flowers, the nectar, is the material from which honey is made; and honey is the only food of bees in a state of nature; honey is for them a matter of life and death. They drink the nectar, convert it into honey, and store it in the comb to support life through the winter. (2) Pollen is the source of the "bee bread" on which the young bees are fed. (3) The whole duty of worker bees — to which they devote incessant labor so long as they live — is to bring nectar and pollen to the combs. (4) The whole anatomy of a worker is an apparatus for extracting, carrying and converting the food that is found in flowers. The mechanisms and instincts of a bee are all directed to one end: making successful visits to flowers. (5) All insects that depend on flowers for a living are, like the bees, engaged in the most serious business of their lives when they visit blossoms: if they do not secure food, they die. And it is equally true of all those flowering plants which depend on insects for pollination that they will die if they do not persuade the insects to visit them. Flowers and insects are engaged every minute of their lives in an unrelenting struggle to exist. If we find them adapted to each other's needs, we can be sure that the adaptation is not a chance and not a joke; it must be a result that has evolved in the course of the long ages of fierce competition to survive. .^sac.?^. "^^5-_ "One Way Passage" of bee through lady-slipper flower. Think of a flower whose stamens "wither before the pistils are ripe for pollen. It can never fertilize itself. The species would die next year if the blossoms did not succeed in entic- ing bees to come to them. A bee has been visiting blossoms in which the stamens have skilfully deposited pollen on her head; she comes to these waiting pistils that are surrounded by dead stamens; she rubs off pollen on them; the flowers are fertilized. No botanist can conceive that a flower has had this remarkable adaptation from the beginning of time; it must have evolved at some period in the history of the species. And there is no way to imagine the evolution except to suppose that all flowers which varied toward this arrange- ment were more likely to have descendants that would con- tinue to vary still further in that direction. We can only imagine that the species was thus transformed by adjusting itself to the tastes of insects. Look at a flower which does not open imtil nightfall. It has no gay colors, for they would not be visible; it has the light yellow color that is most prominent in the starlight; it has a strong odor; its nectar is at the bottom of a long tube. It could never have been developed by its need of bees or wasps. Its color, time of opening, odor, position of nectar — all are adjustments to invite a certain kind of night-flying moth. All its structure and habits have evolved as a response to what this moth desires. There are many plants that have developed ways of fenc- ing out unwelcome ants from the store of nectar — barriers of bristly or tanglefoot hairs. Yet these flowers are so con- structed as to admit the long proboscis of the bee. They have been shaped in a complicated and accurate way by the attacks of enemies and the visits of friends. In some flowers the petals form a cap over the stamens, and this cap is so delicately adjusted that it is thrust aside by the landing of a bee. Instantly the released stamens fly up, strike the bee in the chest, and dust her with pollen, which will fertilize the next flower she visits. Another similar arrangement is a set of stamens that fly up and strike when their base is touched. One of the set of stamens in another flower is provided with a trigger, so set that when the bee's proboscis stretches down for nectar it strikes the trigger and sets all the stamens to vibrating. When you see an orchid in a florist's window, you are look- ing at one of the family of plants that have gone furthest in inventing machinery to work tricks on bees. One of them actually provides a pool of water, on the brink of which is some food that bees are eager to gnaw — so eager that they often push each other into the water! When their wings are draggled, they can leave the flower only by a tunnel near the overflow spout. In this tunnel the pollen is stuck to their backs, and so will be carried to another flower and fertilize it. In some of our American swamps there is a delicate little flower called "sundew," because on the surface of its leaves there are drops of sparkling white. These drops are so sticky that they can hold on to the feet of insects; the hairs on the surface of the leaf then fold over one by one and strangle the insect; the plant digests its' victim. It has evolved a trap and digestive fluids that enable it to eat meat. Many other plants, of very different kinds, have developed other methods of catching and eating insects. For example, the butterwort — which has to rely on insects for carrying its pollen — captures other insects by snapping leaf-edges over them while their feet are caught in a viscous fluid. May, 1932 EVOLUTION Page five There are African plants that have inunense pulpy blos- soms a foot in diameter — ugly in shape, unpleasant in color, and smelling like rotten meat when the pistils need pollen. They are disagreeable to human beings, but flies caimot resist the odor. Flies visit flower after flower, carrying the pollen that clever stamens load them with, brushing off the pollen on the eager pistils. The plant b a swindler; for it promises carrion on which flies can lay eggs, but it gives nothing. This curious adjustment of a flower to meet the instinrts of flies can only be a produrt of gradual evolution. Another rascally flower, in England, plays another kind of confidence game. It coaxes flies to crawl down its throat. They pass quite easily through a ring of hairs that point downward, but they cannot climb out again because those same hairs are now pointed at them and block the way. A fly thus imprisoned must wait until the stamens ripen and dust him with pollen. Then the flower pays its bill with a few drops of nectar; the hairs shrivel up; the fly escapes and soon is down the throat of another flower that captures it and appropriates the pollen it brings. If all flies were teachable and would not venture a second time into the kind of flower that had deceived them, no such trick could have evolved. Flowers have been adjusted to the peculiarities of insects. Sometimes the relation between flower and insect is roman- tically useful to each party. An illustration is a yucca called Spanish bayonet that grows throughout the Southwest. It is entirely dependent for fertilization on a small white moth which collects pollen, carries it to the pistil of another plant, and there tamps it down carefully. Why is the moth so ob- liging? Because she is making a place to lay an egg. When the egg hatches, the larva eats some of the seeds, but not all. Such a marvelously exact adjustment of plant to insect seems purposeful. It is hard to believe that the moth has not reasoned out what she is doing. But of course she has not done, she could not conceivably do, anything of the sort. For every such provident action by an insect is known to be a matter of inherited instinct, which is obeyed without any knowledge of what the result is to be. The instinct could only have been developed by a process of evolution, in which the favorable variations of stamens and pistils and egg-laying desire were adjusted to each other. The plant that furnished more enticing pollen would have more descendants; its type would increase in numbers and would tend to produce still more enticing pollen. Likewise the moth that managed the pollen best was more likely to have successful descendants. Each plant or insect that inherited a tendency toward better co-operation was more likely to have offspring, and these descendants were increasingly likely to inherit the traits that made co-operation still nearer perfect. This theory can explain every case of the adaptations of plants to fertilization by insects. No other theory can account for the adaptations. If there were a botanist who rejected the theory because it seemed too miraculous, he would have to do his scholarly work in the dark. All his fellow botanists live in the light of a theory that helps them understand how nature operates. They can see how insects made the flowers. The Tale of the Horse By ALLAN BROMS /^UTWARDLY we see little likeness between man and not even recognised as an early horse. Now, however, we ^^^ the horse, but inwardly they are much alike. We see, have a very complete fossil record, largely dug out of our outwardly, that the horse has four legs and man but two. Western bad-lands, where the arid soil lacks grass roots to What we forget, for the moment, is that man's arm was, not long ago in his evolutionary history, just a front leg which has become arm only recently by his uprearing to the erect attitude. But let a horse uprear that way, then look through him to his skeleton, and you will see the resemblance in nearly every part. Proportions have changed, especially in the skull, and the horse has lost some teeth, and leg and arm bones. Otherwise they are strikingly alike. At the American Museum of Natural History you can make this comparison, for they have mounted the skeletons of a man and a rearing horse side by side. The marked likeness shows our remote kinship, while the differences are important in their emphasis of the recent evolutionary changes which made man a man and the horse a horse. But here I will tell only The Tale of the Horse. The horse is distinctive in having but one toe to each foot and in his unusual teeth. Both are parts of the same story. Already, back in 1870, Thomas Henry Huxley, the great evolutionist, realised what that story must be and fore- told that we should find the fossil remains of a series of in- creasingly horselike creatures that began with a normal five- toed animal having just ordinary mammal teeth. At that Courtesy Amerian Museum of Natural History time only one fossil of this series had been found, but it was Modem Horse Compared with his early ancestor, Eohippus. Page six EVOLUTION May, 1932 bind It together and the occasional rainstorm torrents cut the loose soil away quickly, exposing the fossil bones. Dozens of species have been found, most of them side branches on the family tree of the horse. We must stick to a very few along the direct line of descent. Eohippus, mean- ing the "dawn horse," is the earliest, living during the Eocene Epoch, some fifty million years ago, in our Western states, where the evolution of the horse seems to have occurred. He was somewhat larger than a big cat and had an arched back. However his feet and teeth were not cat-like, but belonged to a browsing, hoofed animal. There were not five toes on a foot, he was too fat along in his evolution for that, but he did have four on each front foot and three on each hind foot. His brain was well developed for his time, a sure sign that he was active and swift, to make up for his smallness. From this beginning, we can now trace the changes that came on progressively up through the geological epochs, which for us means up through the geological strata or layers of the earth crust, for the top layers are of course most re- cent. There was an increase in size, but only up to a limit consistent with swiftness. Orohippus, the "mountain horse", and Epihippus, the "upon horse", were just a bit larger than Eohippus. By the Oligocene and Miocene Epochs, about twenty million years ago, Mesohippus and Miohippus were already the size of sheep, and though they had three toes on each foot, the two side toes were getting smaller and much of the weight was carried on the middle toe. Hypohippus came a bit later, as large as a pony, its middle toe looking more like a hoof. And so time and change went on until the horses of today have nearly lost their side toes. I say, "nearly lost" them, for remnants remain as the two splint bones now entirely buried in the flesh. Now and then some horse of today reverts to his ancestors and is born with extra toes on his feet. Julius Caesar owned such a horse and more are on record. You may talk about your old families, but none can ride the high horse on the horse; he has a pedigree that stretches back at least fifty million years. But properly, like other folks with ancestors, he has little reason to take pride, for he had nothing to do with it himself. After all, we are all Smu/l 4-Tord UorifS' \STvalI i Fofi \ Lar^t i-Totd \ Lar^t: l-Toed Orchippui- Epihtppui Mnohtppui AjicmUli'ium Mype/iipptii ParaJiippus Mtr^entppui Proto/lippui Pttonippu H'ppidiun Onohippidiu^ - - — (S^outfi America Hippu n i: '(Europe aii-f D/orlri America)- ^ ^Nartlt America. Asia and\£urope)-\ (NcrU AmeLct) ' (Ka,,), America.)- H -•*-«|B . . (No-rf America)- -I-- - ]'* - - (A^m/ri America)- '- - -,- - ■ lS)iatli America f V ■ -( hotlh America .Ana. Eurbpc and A/aiM A^nca)- > {A'ef:r> 1,11.1 Sai^rf' An iiiia |/i]/fl. Furope i^iid Af>, Ccurlcsy American Muieum of Natural History Evolution of Hind Foot of Horse Eohippus, Mesohippus, Miohippus, Merichippus, Hipparion, Equus. Courtesy American Museum of Natural History Geological and Geographical range of ancestors of horse. Black lines show life span of each genus. Dots, show line of descent. creatures of conditions, made by our environments which make demands that we must needs meet, or die out. If our variations change us in the right directions, we survive, if not, our careers end. A change of climate made the horse. When Eohippus made the start, our Western country was low and swampy, just emerged from the sea, for the earth crust here was rising. The climate was moist and the country forest-covered. In these woods, Eohippus hid, alert and quick on the get-away when he was discovered. His coat may have been striped like a zebras to help him hide. His wide, three- and four-toed feet kept him from sinking into the soft ground. He browsed on leaves, which are soft, so his teeth were a browser's teeth, more like those of a tapir than a modern horse. But not only were the swampy forest lands rising; a mountain range was being uplifted to the West, cutting oil the moist winds of the Pacific, causing a dry climate which discouraged the forests. Slowly the woodlands gave way to the grasslands, and the horse found himself out in the open, exposed to many dangers, among them a shortage of leafy food. To survive in this environment, he had to acquire speed for escape and for rapid ranging for his food supply, and had to develop teeth for grinding grasses. The horse perforce became a grazing animal instead of a browser. His teeth dis- close that conclusively. Up front they became sharp for cutting. Then came a toothless space, where we place our bridle bits. And way back, where the jaws have a strong leverage, came the grinders. They became strong, fitted for tough, hard food. The grinders have rough surfaces of com- plex pattern, due to unequal wearing down of the twisty alternating edges of glassy-hard enamel and the soft dentine and cement between. In the early horse, the surface patterns were simple, but as they evolved, the patterns became complex and more horse-like in the modern sense. Also they became longer in root and crown, permitting them, after their ori- ginal growth to maturity, to move instead of grow outward for many years as their surfaces wore down. Altogether, the teeth became fit for cutting and grinding great quantities of May, 1932 EVOLUTION Page seven hard and relatively innutritious grasses of the plains, instead of the soft green leaves of the forests. Necessarily the horse, in order to survive, eventually had to become a grazer with the new kind of teeth. But old ways cling and some horses remained browsers in the remnants of forests that lingered for a long time. Nature tried out both experiments, but finally the drying climate rendered a decision in favor of the swift, grazing plains horse that we know. For the horse was gaining swiftness. Increased size helped, but the changes in his leg machinery were also important. Eohippus was really heavyfooted, for he had a lot of bones down in his foot. But evolution slowly got rid of this excess weight, making the horse literally light-footed. If you want to know how foot-weight handicaps, tie weights on your ankles and try to run. Another aid was that even Eohippus walked on his tip toes, for the horse's hock, half way up his leg, is really his heel. On the dry, grassy plains, the ground was hard, and even the narrow hoof of the middle toe would not sink in it. Besides there was less danger of turning the ankle and other joints on rough ground when the wide foot had been gotten rid of. The joints themselves also changed to prevent turning the ankles and similar injuries. With such joints, he need put forth no effort to keep his legs straight sideways, all his muscles can be devoted to moving forward, to give him speed. Mechanically, he is a marvelous adaptation. He is "on his toes," light-footed, without waste muscles, strong and full-lunged to travel fast and far, to escape his enemies, to cover a wide grazing range. Nature made parallel experiments with several relatives of the horse who were also having a bad time of it in the new hard conditions. Among them was a rhinoceros, small and horse-like, swift on his feet, but somehow not good enough to survive in the severe struggle. Some of the re- latives went in for brainless bulk, the heavy-footed Titan- otheres for instance, but they starved to death on the widen- ing grasslands, there being just too much bulk to feed. An- other relative, the tapir, had specialised too well, found him- self unable to adapt hmiself to the new world, and nearly died out. In the end. the horse also died out in America where he had evolved, but not before he colonised Asia and Africa with wild species such as the ass and zebra and of course the direct ancestors of our modern horses, whom man has so changed that we hardly know what they looked like. At first, for perhaps fifty thousand years, man just hunted the wild horse for food, and but recently learned that the horse was worth more alive than dead, when he harnessed the horse's strength, placed his burdens on the strong back and finally mounted there himself adding greatly thereby to his own powers and prowess. It can safely be said that, without that humble burdenbearer and mount, man could not have built Western civilization, for his own puny strength was unequal to the tasks he undertook. Having domesticated the horse, man took him along to every corner of the globe, — repeopling (or should we say "rehorsing") North and South America. He also remade the horse by selection to suit his own purposes: the heavy Percheron draft horse, a mountain of strength, that delicate jpeed-machine, the race horse, and the tough little Shetland Pony, sure-footed, heavy-coated, fit to survive where going is hard. But now that man has built himself new horses of steel, machines that swim or fly, that eat coal or oil, that can be given any strength and much greater speeds, man is discharging his good servant, Old Dobbin, to a lesser place in the world. For man, as master, remakes his world to meet his own desires. He became master by developing a hand instead of a hoof, but that is another story. However, let us not take too much pride in that, for we are just the lucky favorites of fortunate circumstances that made us into men. This Tvas a radio talk by Mr. Broms. He speaks over WOR every Saturday at 6:30 P. M. Listen in Formations in We5leni.Unitek Mesotlippus Three Toes Side Iocs •vA lOuthing llwgroundi ,pl„l ..<;■-' d,(,l Ttiree Toes Side loti leufhing Ihr jfOund /^ If.-, s'.'d,,.,, M^ Short _^ Crowned, ^'^! wirhoui Cemenr 'b'@ Hvpoiheiiidl AtKcstor5 with hive locj on tath Foor 2nd Teeth like tho^e of Monkeys eic The Premobr Teeth become more sod more like true mola's Courtesy AmcrUan Museum of Natural History Page eight EVOLUTION May, 1932 Parasitology Shows Kinship of Monkey and Man By ROBERT HEGNER Professor of Protozoology in the Johns Hopkins University School of Hygiene and Public Health npHE association of two types of animals in nature is a ■*■ very common phenomenon. In many cases this associa- tion does no harm to either party and may even be mutually beneficial, but occasionally, just as in human society, one member of the association lives at the expense of the other. Such an organism is known as a parasite and the animal it lives on is called the host. Animal parasites belong principally to three groups in the animal kingdom, protozoa, worms, and insects. Everyone is familiar with worms and insects, but protozoa are invisible to the naked eye and hence are never seen except through a microscope. I shall refer in the following paragraphs only to the protozoa that live in monkeys and man. Protozoa are the most primitive of all animals. They dry up very quickly and die if they are deprived of water, hence they are to be found orJy in ponds, streams, lakes, oceans, etc., and in places that are always moist. Vast numbers of protozoa live in both fresh water and salt water. These are called free-living protozoa. Other protozoa, the parasites, live inside of the bodies of animals that live on land, and both inside and outside of animals, such as fish, turtles and whales, that live continuously in the water. Every species of animal that has been carefully studied has been found to harbor protozoa within its body. In some cases, every individual animal belonging to certain species is para- sitized. For example, certain white ants or termites, have their intestines loaded with protozoa that aid in the digestion of their food. This may be considered the normal condition for the white ants. The white ants die if they are deprived of their protozoa, hence every living termite of this type must be a host to large numbers of protozoa. Among other species of animals, parasitic protozoa may or may not be present. Usually the life of the host does not de- pend on the protozoa nor do the protozoa injure the host perceptibly. As a matter of fact, most protozoan parasites appear to be harmless, a sort of equilibrium having become established between the protozoa and their hosts which allows the protozoa to live and reproduce successfully but does not inconvenience the host to any extent. A few protozoa are harmful to their hosts and are said to be pathogenic. Among the pathogenic protozoa of man may be mentioned those that are responsible for amoebic dysentery, malaria, kala-azar, and African sleeping sickness. Domesticated animals are injured by such protozoa as those that cause coccidiosis in chickens, Texas fever in cattle, and sarcosporidiosis in sheep. The protozoan parasites of man have been studied more thoroughly than those of any other animal. They can be separated conveniently into two types: those that live in the digestive tract and are commonly called intestinal protozoa and those that live in the blood and are referred to as blood- SCIENCE LEAGUE OF AMERICA Champions Freedom of Science Teaching. Particulars from Maynard Shipley, Pres., 830 Market Str., San Francisco. inhabiting protoza. The protozoan parasites of monkeys and many other lower animals have also been carefully studied. The following table presents in orderly fashion the names and location in the body of the protozoa that are known to live in monkeys and man. Type of Present in Scteutijic Name Prototoon Localization Man Monkey Trichomonas buccalis Flagellate Mouth Yes Yes Endamocba gingivalis Amoeba Mouth Yes Yes Giardia lamblia Flagellate Small intestine Yes Yes Isospora hominis Coccidium Small intestine Yes No Endamoeba histolytica Amoeba Large intestine Yes Yes Endamoeba coli Amoeba Large intestine Yes Yes Endolimax nana Amoeba Large intestine Yes Yes lodamoeba wiUiamsi Amoeba Large intestine Yes Yes Dientamoeba fragijis Amoeba Large intestine Yes Yes Trichomonis hominis Flagellate Large intestine Yes Yes Chilomastix mesnih Flagellate Large intestine Yes Yes Embadomonas intestinalis \ Flagellate Large intestine Yes Yes Enteromonas hominis Flagellate Large intestine Yes Yes Balantidium coh Ciliate Large intestine Yes Yes Troglodytella abrassarti Ciliate Large intestine No Yes Troglodytella gorillae Ciliate Large intestine No Yes Trypanosoma gambiense Flagellate Blood stream Yes Yes Trypanosoma rhodesiense Flagellate Blood stream Yes Yes Trypanosoma cruzi Flagellate Blood stream Yes Yes Leishmania donovani Flagellate Blood and tissue Yes No Leishmania tropica Flagellate Blood and tissue Yes No Leishmania brasiliensis Flagellate Blood and tissue Yes No Plasmodium vivax Sporozoon Blood ceUs Yes Yes Plasmodium malariae Sporozoon Blood cells Yes Yes Plasmodium falciparum Sporozoon Blood cells Yes Yes Babesia pitheci Sporozoon Blood cells No Yes Sarcocystis (?) Sporozoon Muscle tissue Yes Yes Trichamonas vaginalis Flagellate Vagina Yes Yes This list is not final since we are still studying these or- ganisms and continually learning more about them. How- ever, on the basis of our present knowledge, we may state that of the twenty-eight species of protozoa listed, all but three have been reported from man and all but four have been found in monkeys. This condition is very different from that encountered when one compares the protozoa of man with those of any other animal. For example, the protozoa that have been reported from the pig include the following: 1) Eimeria debliecki — Coccidium 2) Endamoeba polecki — Amoeba 3) lodamoeba suis — Amoeba 4) Trichomonas suis — Flagellate 5) Balantidium coli — Ciliate 6) Trypanosoma brucei — Flagellate 7) Trypanosoma evansi — Flagellate 8) Babesia sp. — Sporozoon 9) Sarcocystis sp. — Sporozoon Only one of these is known with certainty to occur in man, namely Balantidium coli, in spite of the fact that man and pig are very closely associated and must often be inoculated with each other's parasites. A similar condition is met with when the protozoan parasites of man are compared with those May, 1932 EVOLUTION Page nine of dogs, cats, tats, mice, horses, cattle, and other animals closely associated with man. Protozoa that live in man are practically unknown among wild animals. The significance of this situation is made clear when the parasites of nearly related animals are compared. Suffice it to state that the more closely related animals are according to their arrangement in the animal series on the basis of organic evolution, the more nearly similar are their protozoan parasites. We know this to be true. These facts can be stated in another way, namely, the more alike the protozoan parasites of two species of animals are, the more nearly are the two species related. Hence the extraordinary situation as regards the protozoan parasites of man and monkeys noted above can lead to but one conclusion, and that is, that man is more closely related to monkeys than to any other type of lower animal. The data obtained from our studies of proto- zoan parasites thus add very important evidence of the kinship of monkeys and man to that already supplied by anatomy and embryology. Those who wish further information on this subject are referred to the following books and magazine articles. The evolutionary significance of the protozoan parasites of mon- keys and man. By Robert Hegner. Quarterly Review of Biology, Vol. Ill, June 1928, pp. 225-244. A comparative study of the intestinal protozoa of wild monkeys and man. By Robert Hegner and H. J. Chu. American Journal of Hygiene, Vol. XII. July 1930, pp. 62-108. Protozoology. A reference book in two volumes by C. M. Wenyon. 1926. Human Protozoology. By Robert Hegner and W. H. Taliaferro. 1924. These drawings were all made from specimens that had been fixed on glass slides and stained with haematoxylin. They are greatly enlarged. 7 Protozoan parasites that do not occur in both man and monkeys. — 1. Troglodytella, a ciliate that lives in the large intestine of monkeys but not of man. — 2. Isospora hominis, a cocci- dium from the small intestine of man, but not yet reported from monkeys. — 3. Babesia parasites like those foimd in the red blood corpusc- les of monkeys but not in man. EXPLANATION OF FIGURES Flagellates that occur in both man and monkeys. — 1. Trichomonas, similar to species that occur in the mouth, large intestine and vagina. It is not known for certain whether these flagellates are harmful or not. — 2. Chilomastix, an inhabitant of the large intestine. Its patho- genicity is doubtful. — 3. Giardia, a flagellate that lives in the small intestine and prob- ably sometimes gives rise to "flagellate diarrhea". — 4. Trypanosome flagellates that cause African sleeping sickness. — 5. Embadomonas, a harmless inhabitant of the large intestine. — 6. Leishmania, a flagellate causing kala-azar and oriental sore. Protozoan parasites that occur both in man and monkeys. — 1. Endamaeba coli, an amoeba from the large intestine. — 2. Balantidium coli, a ciliate that lives in the large intestine where it brings about a type of dysentery. — 3. A malarial parasite within a red blood corpuscle. — 4. Spores of sarcosporidia ob- tained from muscle tissue. High School Biolofy Teachers find Evolution useful. It gives their students a larger intere't in the subject than simply making a required grade in school. Scores of teachers in half a dozen States already use it and recommend it. Try this ^ issue on your students. Simply write us how many copies to send you (stating what position you hold and give your address in full) . You sell Evolution to your students at 10c and remit to us at the rate of 8 1-3 c. per copy. Address: Evolution. In Making Your Will why not remember Evolution with a be- quest? Let the money that you leave be used to help free the human race from the bondage of superstitions, so as to help offset the millions that are being bequeathed to perpetuate the authority of dogmas. Simply state in your will: "I give, devise and be- queath the sum of dollars to the Evolution Publishing Corporation, a corpora- tion orj^anized and existing under the laws of the State of New York, or its successors." Public Libraries offer a wonderful opportunity for popular education. Many would read Evolution in a Library, who would hesitate to read it at home because of possible trouble with their folks. Once they become interested through this journal they may draw science books from the library, and a new life open for them. For every dollar that you contribute for this purpose we'll put a public library on our mailing list. Simply specify "Library Fund" with your remittance to Evolution. Page EVOLUTION May. 1932 The Story of the Grand Canyon By HUGH F. MUNRO JOHN Burroughs tells us that the West is full of Geology. must be at the bottom where the Colorado river is busy with So is the East for that matter, but in the West we see the continuation of it. At the river level we are standing Mother, Nature in her youth, unclothed, raw, angular. In on the very cellar floor of the earth, so far as the geologist the East she has taken on a mature rotundity and clothed has been able to read the story, the Archeozoic, herself with a becoming mantle of green. In the eastern No recognizable fossils have been found in the Archeozoic landscape Hit predominates while the West is stark and bare, rocks, although there is indirect evidence that life already less modified by the softening influences of plant and animal life. The West is the paradise of the geologist, for in it the great earth book has been stripped of its covers and its pages lie open for all who care to read and take the trouble to understand its story. More pages of the earth's history are exposed in the Grand Canyon of Arizona than in any other part of the world, yet half of the chapters are missing. To the tourist the Grand Canyon is merely a great gash in the earth's surface about a mile and a quarter deep, from ten to twelve miles wide and over two hundred miles long. The south rim at El Tovaris is 6866 ft. above sea level, the north rim 1000 ft. higher. Resisting the temptation to dwell on the sublimity of the awe-inspirmg spectacle which is felt as well as seen we turn at once to the study of its history. Aided by rain, frost, wind and chemical action, the Colo- rado river with its tributaries has been at work for ages cut- ting away the rock and carrying the debris toward the sea. In the absence of the retarding effect of vegetation, rain cuts its own channels which become deeper year after year, a pro- cess that can be seen on any uncovered country road. In the West it is not unusual to cross the dry bed of a river that after a few hours of rain will become a turbid torrent flow- ing swiftly in narrow channels and carrying a heavy load of scouring material. The rivers all over this region cut out and flow in gorges with almost perpendicular walls. Descending into the Canyon by the Bright Angel trail. even the most casual observer can see in the varied colors of the rock layers that the Canyon has a history, and little Ph