s as transition-types
leads ad absurdum. The close structural relationship between man and
monkeys can only be understood if both are brought into the same line
of evolution. To trace man's line of descent directly back to the old
Eocene mammals, alongside of, but with no relation to these very similar
forms, is to abandon the method of exact comparison, which, as Darwin
rightly recognised, alone justifies us in drawing up genealogical trees
on the basis of resemblances and differences. The farther down we go the
more does the ground slip from beneath our feet. Even the Lemuridae
show very numerous divergent conditions, much more so the Eocene
mammals (Creodonta, Condylarthra), the chief resemblance of which to man
consists in the possession of pentadactylous hands and feet! Thus the
farther course of the line of descent disappears in the darkness of the
ancestry of the mammals. With just as much reason we might pass by the
Vertebrates altogether, and go back to the lower Invertebrates, but
in that case it would be much easier to say that man has arisen
independently, and has evolved, without relation to any animals, from
the lowest primitive form to his present isolated and dominant position.
But this would be to deny all value to classification, which must after
all be the ultimate basis of a genealogical tree. We can, as Darwin
rightly observed, only infer the line of descent from the degree of
resemblance between single forms. If we regard man as directly derived
from primitive forms very far back, we have no way of explaining the
many points of agreement between him and the monkeys in general, and the
anthropoid apes in particular. These must remain an inexplicable marvel.

I have thus, I trust, shown that the first class of special theories
of descent, which assumes that man has developed, parallel with the
monkeys, but without relation to them, from very low primitive forms
cannot be upheld, because it fails to take into account the close
structural affinity of man and monkeys. I cannot but regard this
hypothesis as lamentably retrograde, for it makes impossible any
application of the facts that have been discovered in the course of
the anatomical and embryological study of man and monkeys, and indeed
prejudges investigations of that class as pointless. The whole method is
perverted; an unjustifiable theory of descent is first formulated with
the aid of the imagination, and then we are asked to declare that all
s