In the paper to which I have referred, Professor Bischoff does
not deny the second part of this statement, but he first makes
the irrelevant remark that it is not wonderful if the brains of
an orang and a Lemur are very different; and secondly, goes on to
assert that, "If we successively compare the brain of a man with
that of an orang; the brain of this with that of a chimpanzee; of
this with that of a gorilla, and so on of a Hylobates,
Semnopithecus, Cynocephalus, Cercopithecus, Macacus, Cebus,
Callithrix, Lemur, Stenops, Hapale, we shall not meet with a
greater, or even as great a, break in the degree of development
of the convolutions, as we find between the brain of a man and
that of an orang or chimpanzee."

To which I reply, firstly, that whether this assertion be true or
false, it has nothing whatever to do with the proposition
enunciated in 'Man's Place in Nature,' which refers not to the
development of the convolutions alone, but to the structure of
the whole brain. If Professor Bischoff had taken the trouble to
refer to p. 96 of the work he criticises, in fact, he would have
found the following passage: "And it is a remarkable
circumstance that though, so far as our present knowledge
extends, there IS one true structural break in the series of
forms of Simian brains, this hiatus does not lie between man and
the manlike 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 manlike ape, on the