result that in spite of being protectively colored, out of 32 green caterpillars at the beginning of the season only two a number just equaling that of the unprotected brown caterpillars -survived to pupate with the latter." 38

It is possible then to overemphasize the value of protective coloration. Other observers lay stress on mimicry, the close resemblance of one animal to another: a fly to a dangerous wasp, a bug to another disliked by birds because of some very disagreeable odor, a moth hardly to be distinguished at rest from a dried leaf. Though it may not be possible to explain all these phenomena or state their meaning they must have some significance. Moreover, we know that some human beings are more likely to take certain diseases than are other persons and to suffer more from them. If the disease results fatally there may come in time the elimination of the susceptible stock. It would seem then that natural selection is a real factor in life even though its whole rôle is not understood and is perhaps exaggerated.

Biology and paleontology have advanced so rapidly that it is now possible to outline the process of evolution. In the earliest of the stratified rocks, the Azoic, there are no signs of life. This does not necessarily mean that no life existed, but that the early forms of life were simple masses without shells or bones which might be preserved. At the bottom of the animal scale are the one-celled forms called protozoa. Of these the ameba (.01 of an inch in diameter) which is common in vinegar, will serve as an illustration. All we can see is a membrane filled with liquid and inclosing a nucleus. The ameba may slowly move by changing its shape. If it comes in contact with 38 MOORE, E. C. In Old Penn. Dec., 1914, p. 361.

a particle of food it wraps itself about it and gradually absorbs it. In the ordinary sense there is no specialization

of organs.

Higher than the ameba stand the animals made up of many cells arranged in two layers. The hydra is a cylinder closed at one end where it is fastened to the rocks. At the open end of the cylinder are tentacles which by their motion cause the currents of water to enter the cylinder thus carrying food. The outer cells are protective, the inner layer digests the food.

Next in the scale are the worms in which we find a series of cylinders fastened together. These segments are alike in structure and function. This form characterizes the great mass of invertebrates. Crabs and lobsters as well as beetles and butterflies are built on this plan and are characteristic of the Paleozoic age.

The fishes are the first animals with backbones. The earlier types were covered with heavy coats of mail like the gar pike of our inland lakes. The shark represents perhaps the basic form, a great mass without sharp division of head, body and tail.

The next stage is represented by amphibious creatures which have gills during the earlier stages. Typical of this stage are the salamanders and frogs. These yield place to the reptiles, the lizard, bearing close resemblance to the early type. Snakes are but degenerate lizards. From the reptiles it is but a short step to the birds, the scales being modified to feathers, the fore legs to wings. Here too transitional forms survive like the apteryx of New Zealand, while the penguins and ostriches are wingless in so far as power of flight is concerned. The Mesozoic age is thus one of transition.

Lowest among the mammals are the Ornithorhynchus or

duckbill and its relative the echidna which superficially resembles the hedgehog. Both these lay eggs. The next stage is represented by the marsupials, the so-called Tasmanian wolf, the Australian kangaroo and the American opossum. This brings us to the true placenta-bearing mammals divided into many orders such as the rodents: the rats, mice, squirrels and rabbits; the carnivora: lions, tigers, wolves and seals; and finally to the Primates, at the head of which is man. This development of mammals takes place during the Cenozoic or Tertiary age though clear records of man are not found till the recent or Quaternary. Such is the order of existing life. The same story may be read in the rocks where too are preserved many intermediate forms or "missing links" which prove beyond reasonable doubt the gradual evolution of the various forms of life.

There is no reason to except man from this series. "The supreme place is given to man on account of four and only four characteristics; these are (1) an entirely erect posture, (2) greater brain development, (3) the power of articulate speech, and (4) the power of

Man's nearest relatives are the anthropoid apes of which there are four groups: (1) marmosets, (2) tailed monkeys, (3) baboons and (4) apes (gibbon, orang-outang, chimpanzee and gorilla). The gibbon stands erect using its long arms to keep its balance as it walks. If it goes on all fours the face is parallel with the ground. In the orang-outang the brain development has so changed the position of the head that on all fours it can scarcely bend back its head far enough to look straight ahead. The chimpanzee is still more manlike though its feet are still 39 CRAMPTON, H. E. Doctrine of Evolution, p. 159.

like hands. In height it is often five feet, or more than some races average. Still closer to man is the gorilla. The brain of the apes is highly developed, averaging between 400 and 500 c.c., though chimpanzees have been found with brains as small as 200 c.c. and gorillas with brains of 610 c.c. To meet human demands it is estimated that the brain cannot be less than 950 c.c. It has been found that the blood of the higher apes is almost identical with human blood. It seems obvious that the differences between men and apes are those of degree and not of kind.

A second line of evidence comes from the development of the individual. All animals, including man, begin as single cells. In the course of development the organism recapitulates in striking fashion the evolution of the race. The microscope shows that the cell is much like the simplest forms of life. At one stage the human embryo has a fish-like heart, brain, muscles, alimentary tract and even gill slits in the sides of the neck. Later on it closely resembles the embryos of the rabbit or cat. Then it bears close resemblance to the embryo of the ape and is covered with a coat of hair which is shed before birth. After birth the child holds its legs just as do the apes, the spinal column is a single curve as is that of the ape, while in the adult man it has a double curve. The human infant for a few weeks has a striking power of supporting itself by hanging on a stick. The hairs of the body have the same slant as do those on the apes. Moreover, the various vestigial organs can only be explained on the assumption that once they meant something to man's ancestors. Thus we have the remnants of a second stomach in the vermiform appendix, the muscles that move the ears, traces of an extra eyelid, muscles and bones that once formed a

tail. The conclusion is irresistible that man is a part of the organic world, the result of a long and slow process of change.

From time immemorial there had been found, in various quarters of earth, pieces of stone, some rough, some chipped to sharp edges, some polished which excited much curiosity, and were often called thunder-stones. In Chaldea they were put in temple walls; in Egypt, strung about the necks of the dead; in India, even today, they are to be found on altars. They were considered weapons used by the gods. "During the Middle Ages many of these well-wrought stones were venerated as weapons, which during the war in heaven' had been used in driving forth Satan and his hosts . . . in the twelfth century a Bishop of Rennes asserted the value of thunder-stones as a divinely-appointed means of securing success in battle, safety on the sea, security against thunder, and immunity from unpleasant dreams." 40 At the end of the sixteenth century Mercati tried to show that they were implements of early man but Tollius in 1649 suggested a more acceptable notion when he said that they were generated in the sky by a fulgurous exhalation conglobed in a cloud by the circumposed humor." 41 In 1715 a pointed weapon of flint was found with the bones of an elephant in London. In 1723 and 1724 Jussien and Labitan in France hit upon the correct explanation and started the study of comparative ethnology. From this time on there was an increasing number both of discoveries and of men who dared defy popular opinion in their interpretations. Geology was denounced as "a black art,” "a forbidden province," " an awful evasion of the testimony of revelation," and even Cowper wrote:

40 WHITE, A. D. o. c., I, p. 266.

41 Ibid., I, p. 267.