the idea of fixity prevailed more among thinkers with a religious bias; but for the most part the theories were debated independently of the tenets of any faith, Christian or other.  There were sceptical defenders of fixity and religious upholders of evolution.  However, in Christian countries, from the time of the Reformation onwards, a change in this neutrality of religion to theories of the living world took place.  As Pascal prophesied, Protestantism rejected the idea of an infallible Church in favour of the idea of an infallible book, and, because it happened that this book included an early legend of the origin of the world in a form apparently incompatible with evolution, Protestantism and, to a lesser and secondary extent, Catholicism, assumed the position that there was no place for evolution in a Christian philosophy.  At the end of last century, and up to the middle of this century, the problem was not raised in any acute form.  The chief anatomists and botanists were occupied with the investigation and discovery of facts, and, in an ordinary way, without taking any particular trouble about it, accepted more or less loosely the idea that species were fixed.  Now and then an evolutionist propounded his views; but, as a rule, he supported them with a knowledge of facts very much inferior to that possessed by the more orthodox school.  Then came Herbert Spencer, reasserting evolution in the old broad spirit, not merely in its application to species, but as the guiding principle of the whole universe from the integrations of nebulae into systems of suns and planets to the transformations of chemical bodies.  Before his marvellous generalisations had time to grip biologists, there came Darwin; and Darwin brought two things:  first, a re-statement of the fact of evolution as applied to the living world, supported by an enormous body of evidence, new and old, presented with incomparably greater force, clearness, patience, and knowledge than had ever been seen before; and, second, the exposition of the principle of natural selection as a mechanism which might have caused, and probably did cause, evolution.

Huxley, as has been shewn, like many other anatomists, was ready for the general principle of evolution.  In fact, so far as it concerned the great independent types which he believed to exist among animals, he was more than prepared for it.  Let us take a single definite example of his position.  In his work on the Medusae, he had shewn how a large number of creatures, at first sight diverse, were really modifications of a single great type, and he used language which, now that all zooelogists accept evolution in the fullest way, requires no change to be understood: