168 A.. A. W.. HUBRECHT. 
the Lemurs differ considerably from Rodents, Insectivores, 
and Primates, but have again great similarity with Perisso- 
dactyles and Artiodactyles (Hquus, Sus, Tapirus) and others. 
Here, then, is a point to which paleontologists should try 
to give particular attention. They might then help us 
to get hold of a clue by which to differentiate the 
early mesozoic pedigree of Ungulates and Lemurs from that 
of the Primates, Insectivores, and Rodents, and by that 
contribute to restore their own belief in the value of onto- 
genetical characters as guides to problems of classification. 
I finally wish to cite the last phrases of Wortman’s so 
exceedingly suggestive paper just alluded to, in which he 
finds it dificult—and I am here in full accordance with him 
—to derive the Primates from the Insectivora. He says: 
“The greatest difficulty in the way of deriving the Primates 
from any form or forms of the Insectivora at present known 
consists in the total lack of prehensile powers of the manus 
or pes. Any group which is placed ancestral to the Primates 
must of necessity be one in which some distinct approach to 
this condition is made, since its possession is one of the chief 
requisites of fundamental importance. . . . With the 
single exception of Lophiomys among the Rodentia, the only 
other living mammals which exhibit prehensile extremities 
are found among the Marsupials, and the evidence points 
very conclusively to the fact that all of them, even those 
with highly modified limbs for terrestrial progression (as the 
kangaroos), are descended from ancestors with grasping 
hands and feet. It is, therefore, not beyond legitimate 
supposition to assume the existence of a very considerable 
croup of ancient Metatherians living within the arctic circle 
during cretaceous time whose manner of life had already 
become arboreal. If such a group did exist it is far more 
likely that the Primates were derived from it rather than 
from the Insectivora or any other group now living.” 
Now the prehensile power of the manus or pes lacking in 
the Insectivora as far as known to us re-appears again, at 
least in the shape of an opposable thumb in certain Amphibia 
