Man and Monkeys 133 
pentadactylous Eocene forms, which may either have led directly 
to the evolution of man (Adloff), or have given rise to an ancestral 
form common to apes and men (Klaatsch’, Giuffrida-Ruggeri). The 
common ancestral form, from which man and apes are thus supposed 
to have arisen independently, may explain the numerous resemblances 
which actually exist between them. That is to say, all the characters 
upon which the great structural resemblance between apes and 
man depends must have been present in their common ancestor. 
Let us take an example of such a common character. The bony 
external ear-passage is in general as highly developed in the lower 
Eastern monkeys and the anthropoid apes as in man. This character 
must, therefore, have already been present in the common primitive 
form. In that case it is not easy to understand why the Western 
monkeys have not also inherited the character, instead of possessing 
only a tympanic ring. But it becomes more intelligible if we assume 
that forms with a primitive tympanic ring were the original type, and 
that from these were evolved, on the one hand, the existing New 
World monkeys with persistent tympanic ring, and on the other an 
ancestral form common to the lower Old World monkeys, the anthro- 
poid apes and man. For man shares with these the character in 
question, and it is also one of the “unimportant” characters required 
by Darwin. Thus we have two divergent lines arising from the 
ancestral form, the Western monkeys (Platyrrhine) on the one hand, 
and an ancestral form common to the lower Eastern monkeys, the 
anthropoid apes, and man, on the other. But considerations similar 
to those which showed it to be impossible that man should have 
developed from an ancestor common to him and the monkeys, yet 
outside of and parallel with these, may be urged also against the 
likelihood of a parallel evolution of the lower Eastern monkeys, the 
anthropoid apes, and man. The anthropoid apes have in common 
with man many characters which are not present in the lower Old 
World monkeys. These characters must therefore have been present 
in the ancestral form common to the three groups. But here, again, 
it is difficult to understand why the lower Eastern monkeys should 
not also have inherited these characters. As this is not the case, 
there remains no alternative but to assume divergent evolution from 
an indifferent form. The lower Eastern monkeys are carrying on 
the evolution in one direction—I might almost say towards a blind 
alley—while anthropoids and men have struck out a progressive 
path, at first in common, which explains the many points of re- 
semblance between them, without regarding man as derived directly 
from the anthropoids. Their many striking points of agreement 
} Klaatsch in his last publications speaks in the main only of an ancestral form 
common to men and anthropoid apes. 
