1897] NOTES AND COMMENTS 153 
evidence adduced by Dr W. B. Scott and others as to the separation 
of North and South America cannot be overthrown by the con- 
clusions drawn from one group of animals, more especially when an 
alternative route of migration will explain the facts equally well, if 
not indeed better. 
THE OLD WoriLp EDENTATE MAMMALS 
WHILE it may be admitted that one swallow does not make a 
summer, it cannot be contended that a single tooth is not amply 
sufficient to prove the existence of the group of animals in the 
country where it was found. And as Dr Wortman expressly states 
that Calamodon ewropaeus—founded on a canine from the Swiss 
siderolithes—is a member of the Ganodonta, there is ample evidence 
of the existence of that group in Europe during the Eocene. Prob- 
ably Dr Wortman is unaware how rare mammalian fossils are in 
those deposits, and why he should make a point of their absence 
from the later European Tertiaries passes our comprehension. With 
regard to Africa, no Eocene or middle Tertiaries are known, and 
consequently no arguments can be drawn one way or another. 
Moreover, it is known that when the later South American ground- 
sloths succeeded in entering the northern half of the New World 
during the Pliocene, they flourished excellently well, and if their 
ancestors reached the South from the North, it is difficult to see why 
the group should have immediately died off in the latter area. 
To our own thinking it is much more probable that the Eocene 
Ganodonts of the northern hemisphere migrated southwards from 
Europe to Africa, and eventually reached South America by that 
route, as appears to have been the case with certain other groups of 
mammals. This, of course, opens up the question whether the Old 
World, so-called Edentates may not after all really belong to that 
group. Without denying the possibility of this, it may be urged 
that whereas the skulls and limb bones of the Ganodonta are 
strikingly like those of the South American edentates, those of 
Manis and Orycteropus are as strikingly unlike. If, therefore, 
they belong to the same stock, they would appear to have diverged 
before the Gancdonta assumed their characteristic type. But as 
this was acquired in the early Eocene, the Edentate origin of 
Orycteropus and Manis seems very problematical. At the same 
time we have at present no other group in which to look for the 
parentage of those strange creatures. 
NEw LIGHT ON THE OVA OF VERTEBRATA 
In the series of observations published by K. Mitsukuri, of Tokyo, 
in the Jowrnal of the College of Science of the Imperial University, 
