EVOLUTION’S SECRET

Evening Star, Issue 20959, 25 November 1931, Page 11

EVOLUTION’S SECRET

MYSTERIOUS AS EVER Professor D’Arcy Thompson, the veteran scientist, made a dramatic pmtest in the Zoology section of the Brit.iVb Association during a general discussion on evolution, says the 4 Morning Post.' “•We have been told,” lie said, “ that rents have been torn in the veil which surrounds the mystery of evolution, and that this has irretrievably destroyed chapters of the Old Booh. That explanation does not suffice for me, and I honestly believe that wo are as ignorant as we were seventy years ago. “ In the great gaps between vertebrates and invertebrates there is no possibility of one passing into the other. “ I am not defying the evidence of evolution, but I believe that any attempt to find an invertebrate which has passed into a vertebrate type is doomed to failure.” Immediately before Professor D’Arcy Thompson’s protest the members had been startled by a statement made by Dr Robert Broom, of South Africa, that ho had solved the origin of mammals. “ We have a complete record of mammals,” he said, “ going back for forty million years. It is the history of tho world.” After discussing how invertebrates had developed into vertebrates, Dr Broom said that there was no further possibility' of new groups or orders of mammals developing. “ There is no reptile alive today,” ho said, “ which can give rise to a mammal; no fish which can become a reptile, and no animal which can become a man. The evolution of reptiles and animals is complete, and for thirty million years no new reptile has appeared in the world.” Professor Julian Huxley, whoso participation in the debate had caused the new Whale Gallery , to become crowded, sugested that most animals seemed to bo subject to a natural adaptability which had nothing whatever to do with heredity or evolution. “Various animals produce horns or claws at certain stages of their growth,” he said, “ simply because they have to. _ They cannot help doing it, and this implies a clockwork mechanism present in the _ germ plasm which operates automatically.” Professor H. Fairfield Osboru mentioned that in Darwin’s time onlv

8,767 species of animals were known, and now there were 65,939. Professor E. B. Boulton, in Ills presidential address to the section, spoko on 4 A Hundred Years of Evolution.’ Discussing the theory of evolution by natural selection as the explanation’of deceptive mimicry in insects, the professor directed attention to certain experiments which threw light on tho brain and senses of vertebrate enemies of insects, and which, he believed, proved beyond doubt that the mind and memory of reptilian and avian enemies were such as one would expect to find in the selective agents which had brought about the evolution of mimicry in insects. A chameleon which, after rejecting a bee which it had captured the moment after its introduction into the cage—■ after this single experience—would never touch another. A lizard which approached a hornet-like Clearwing Moth with the utmost circumspection, and then evidently realising from tho texture that the insect was not a wasp or hornet, proceeded to cat it without further caution, a few days later recognised another at sight and instantly, devoured it. - . Evidence of a different kind, but probably very significant, was provided by the well-known African Honey Guido which directed man to a bee’s nest and was repaid by a meal on the scattered larva?. This bird, when insufficient attention was paid to its directions, became so noisy that game was disturbed. How far the behaviour of the bird was instinctive and how far intelligent was unknown. Ho believed that this and other similar behaviour proved that birds possessed a brain and sense-organs such as would lead them in seeking their food to associate the qualitcs favoured or unfavourable with the appearance, and to remember and apply their export ence; in fact, precisely tho powers re-* quired by a selective agent in building up a mimetic pattern.