is an innovation which is not only opposed to generally and
     justly accepted doctrines, but which is directly negatived by the
     testimony of all original enquirers who have specially
     investigated the matter; and that it has neither been, nor can
     be, supported by a single anatomical preparation.  It would, in
     fact, be unworthy of serious refutation except for the general
     and natural belief that deliberate and reiterated assertions must
     have some foundation.”

The last remarks referred, of course, to the statements of Owen, which had made a great impression at the time and the result of which still lingers in some of the worse-informed treatises attacking evolution.  Huxley gave a lucid account of the general structure and arrangement of the brain in the vertebrate series, explaining the well-known fact that from fish up to man the general ground-plan of the brain is identical, but that there is a progressive increase in the complexity and in the size of some parts compared with others.  Next, he showed that, so far from its being possible to erect any barrier in the structure of the brain between man and the apes, there exists among the mammals an almost complete series of gradations from brains a little higher than that of the rabbit to brains a little lower than that of man.  He laid great stress on

“the remarkable circumstance that though, so far as our present knowledge extends, there is one structural break in the series of forms of simian brains, this hiatus does not lie between man and the man-like apes, but between the lower and the lowest simians; or, in other words, between the old-and new-world apes and monkeys, and the lemurs.  Every lemur which has yet been examined, in fact, has its cerebellum partially visible from above, and its posterior lobe, with the contained posterior cornu and hippocampus minor, more or less rudimentary.  Every marmoset, American monkey, old-world monkey, baboon, or man-like ape, on the contrary, has its cerebellum entirely hidden, posteriorly, by the cerebral lobes, and possesses a large posterior cornu, with a well-developed hippocampus minor.” ...  “So far from the posterior lobe, the posterior cornu, and the hippocampus minor being structures peculiar to, and characteristic of man, as they have over and over again been asserted to be, even after the publication of the clearest demonstration of the reverse, it is precisely these structures which are the most marked cerebral characters common to man with the apes.  They are among the most distinctly simian peculiarities which the human organism exhibits.” ...  “Man differs from the chimpanzee or the orang, so far as cerebral structure goes, less than these do from the monkeys, and the difference between the brains of the chimpanzee and of man is almost insignificant, when compared with that between the chimpanzee brain and that of a lemur.”