CREATION BY EVOLUTION
should require the notes of some immortal angelic observer who had watched the process of evolution for ages and had left us a record of his observations! All our evidence must therefore be indirect and circumstantial, and it may be divided into three main groups—(1) evidence from the systematic relations of allied species, (2) evidence from fossils (palaeontology), and (3) evidence from the development of the individual (embryology). The evidence comprised under the first two heads is presented elsewhere in this book; it is my task to present the evidence or argument from embryology.
The embryological argument rests on a daring hypothesis, which was first clearly expounded by Haeckel in what he termed the jundamental law of biogenetics, which he enunciated as follows: Every animal, in its growth from the egg to maturity, recapitulates the history of the race. Therefore, when we find in the embryo, during its growth, stages that resemble animals lower in the scale of life, this resemblance is regarded as evidence that the animal whose embryo we are studying was derived from ancestors that resembled those stages.
When we take a broad survey of the animal kingdom we find that it can be divided into great primary divisions termed phyla. The bodies of all the members of a phylum are constructed on the same plan. A good example of a phylum is provided by the Arthropoda, the jointed animals. This group comprises all the insects, spiders, mites, scorpions, centipedes, lobsters, crabs, shrimps, barnacles, and water-fleas; in fact, it includes three-fourths of the species of animals now living on the globe. All these animals have, outside their flesh, a hard, shelly skeleton, which is divided into joints by zones of thinner shell, as otherwise the animal could not bend itself or move. All likewise possess several pairs of limbs, which, like the body, are encased in similar armour
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