it.  Later on, Cuvier removed from it these wilder excrescences, and amplified the basis of observation upon which the underlying theory of the unity of type of the skull throughout the vertebrates was based.  Cuvier, however, came to reject the theory, except so far as it applied to the posterior or occipital segment of the skull.  Later on, Owen resuscitated the theory, first throwing doubt on the merit of Goethe, and then suggesting that Oken, instead of relying on the observed facts, had deduced the whole theory from his own imagination.  Owen, although he made no new contribution to fact or theory in this matter, practically claimed the whole credit of it as a scientific hypothesis.

When Huxley took up the subject, the position was that the vertebral theory was in full possession of the field, under the auspices of Owen.  Huxley began afresh from observed facts.  The first object of his investigation was to settle once for all the question as to whether the skulls of all vertebrates were essentially modifications of the same type.  He took in succession the skulls of man, sheep, bird, turtle, and carp, and showed that in all these there were to be distinguished the same four basi-cranial regions:  the basi-occipital, basi-sphenoid, pre-sphenoid, and ethmoid.  These were essentially identical with the centra of the four vertebrae of Oken.  Similarly, he showed the composition of the lateral and dorsal walls, proving the essential identity of the structures involved and of their relations to the nerve exits in the great types he had chosen.  In the series of lectures delivered before the College of Surgeons, he extended his observations to a much larger series of vertebrates, and substantially laid down the main lines of our knowledge of the skull.  In two important respects his statements were not merely a codification of existing knowledge, but an important extension of it.  He distinguished the different modes in which the jaws may be suspended to the skull, and established for these different kinds of suspensoria the names which have ever since been employed.  He proved clearly what had been suggested by Oken, that the region of the ear is a lateral addition to the skull, and he distinguished in it three bones, his names for which have since become the common property of anatomists.  Finally, he made it plain beyond any possible doubt that the skulls of all vertebrates were built upon a common plan.

Having established the facts, he proceeded to enquire into the theory.  There was now a new method for investigating such problems, the method of embryology, which, practically, had not been available to Oken, and of which neither Cuvier nor Owen had made proper use.  By putting together the investigations of a number of embryologists, by adding to these himself, and, lastly, by interpreting the facts which his investigations into comparative anatomy had brought to light, he shewed that the vertebral theory could not be maintained.