39 
endowed than the living, and why should the Mesozoic 
birds possess reptilian structures ? The idea v/hich I have 
formed for myself on this point is that the high organi- 
sation of the reptilia quoted above has been inherited by 
the Aves and Mammals, and that the present less richly 
endowed reptiles are to be looked upon as younger sons 
cut off from the estates of their ancestors by a natural law 
of entail. That the aves and mammalia have actually been 
derived from a reptilian stock seems to me to be probable 
from the changes which the embryos undergo. 
The question so often triumphantly asked by the adver- 
saries of the doctrine of evolution, how is this or that change 
from one form into another produced, seems to me to be 
altogether idle. We know very little of the how or the 
why of any natural process. It is a fact that a grain of 
wheat will produce a blade, and ultimately repeat itself 
many times over; although we cannot tell what are the 
precise forces which regulate its form and development. It 
is sufficient for me to know that these changes actually 
take place, without knowing hovr they have been produced. 
They are altogether unintelligible to me without a belief in 
evolution, of which the very least that can be said is that 
it is a good working hypothesis, which is held consciously 
or unconsciously by most of the leading naturalists of the 
day. 
6. The Antiquity of Man. 
The exploration of the late Tertiary deposits, and more 
particularly of the ossiferous caverns, has made impor- 
tant additions to our knowledge of Man, in Europe, during 
the last two years. The incised figures of rein-deer and 
horses found in the cave of Kesslerloch [Excavation at the 
Kessleiioch, by Conrad Merk, translated by Lee, 3876] 
proves that palaeolithic tribes, allied probably to the 
Eskimos formerly, lived in Switzerland along with the 
extinct mammalia, wffiile the discoveries at Cresswell, 
