EDUCATION BY WIRELESS

Radio Record, Volume II, Issue 51, 5 July 1929, Page 13

EDUCATION BY WIRELESS

The Mechanism of Evolution

[Tse following is the summary of the third W.H.A. lecture on the above subject, to be given from 4YA on Tuesday, July 9, 1929, at 7.80 p.m. 38.-The Lamarckian Factor. FARLY in the nineteenth century, just fifty years prior to the appearance of Darwin’s "Origin of Species," the French zoologist, Lamarck, published a work on zoological phiiosophy which included a clear account of a theory of evolution, which many scientists of to-day still support in a more or less modilied form. . Though Lamarck was a _ brilliantlygifted man and a great observer, his work was much hampered by his poverty and the blinduess which overtook him later in life. I‘urther, the great rench anatomist, soologist, aud palaeontologist, Cuvier, who, at this time exerted a very poweriul influence over scientific thought and was a man of high social standing, was a iirm supporter ot a modified theory of creation to account for the origin of species. Consequently the work of Lamarck, which clashed with the views of his brilliant and influential opponent, was neglected during his lifetime and was not appreciated until many years after his death, Lamarck’s theory of evolution involves two main basie principles, in the tirst place, he believed that the changes which result in the evolution of new iorms are brought about by the direct intluence of the environment acting upon the nervous system. A change in any of the conditions which constitute the environment will cause a need or want to be felt by the organism; and if this want is felt over a long-continued period, a new organ may gradually be developed, or existing organs may be adapted to suit the new environmental conditions. Environment, then, plays just as important a part in Lamarck’s theory as it does in Darwin's principle of natural selection, but there is this great difference between the two theories. Lamarck believes environment actually to cause changes to take plave in the structure of the organism. Darwin, on the other hand, states that from the innumerable variations and changes that happen to occur in any species, those which suit the new surrounding conditions are selected and perpetuated, while the comparatively useless variations are eliminated. The second part of Lamarck’s theory states that once any new character is acquired or an existing one modified by the influence of environment, such a character will be transmitted to successive generations by heredity, till ultimately it becomes an established and characteristic feature of the new species. All biologists agree that there is much truth in the first of these two basic principles: but for it to have evolutional significance, the second principle outlined above must also operate. Here is the point over which much controversy arises. Is it possible that such acquired characters zan be trausmitted by heredity? The geneticists headed by Weismann insist that if the nucleus of the protoplasmie cell itself contains ‘the determin-

ants of hereditary qualities, then ‘since the protoplasm cannot possibly be influenced by the environment of the organism, any characters acquired under its influence during life will not affect the germplasm and will not therefore be handed on to the next generation. If this argument is correct we must regard Lamarck’s theory as disproved, A good deal of experimental work has been done along the line of producing "acquired" characters in animals such as mice, guinea pigs, salamanders and insects, and subsequently testing whether or not these characters may be inherited, Evidence of this sort is sometimesperhaps more usually-in favour of Lamarck’s theory, and sometimes apparently opposed to it. Much of it is inconclusive, as it is difficult to prove that the characters thus artificially induced are comparable with those acquired under natural conditions. Probably geologists and palaeontologists are the strongest supporters of Lamarck’s principle to-day. The geologist looks back through the countless millions of years that make up geological time and sees the slow pulsation of life as it ebbs and flows on its evolutional course. Many of the changes which he sees-often the most profound ones- he can only explain on the assumption that they have been brought about by the direct influence of the great changes in climatic, physiographic and other environmental conditions, which he knows to have occurred again and again through the ages. Many geologists would suggest, for example, ‘that the first land vertebrates originated from a group of fishes away back in the remote period which we term the Silurian, under the compelling influence of adverse climatic conditions to which the survivors were forced to adapt themselves. We know that no one mechanism can account for all the phenomena of -evolution. So geologists believe that, while natural selection is the chief agent in evolution, yet Lamarck’s principle of the more direct action of environment has also been at work. Such, indeed, was the view of Darwin himself.