77 
Japan and elsewliero, some of whicli perhaps this beautiful garden 
contains, originated in polar regions, since allied forms are met 
with in different j)arts of tlie earth, which seem equally to have 
migrated from the north. To take one example — the Sequoias 
or elhuqtonias of California have their nearest and indeed only 
representatives in Ea.stern America and in China and Japan, 
while there are no such trees in Europe, although they are 
perfectly adapted to our climate, and are being introduced into 
this country with success. Eut they existed in circumpolar 
regions during these Tertiary periods of greater warmth, and seem 
to have migrated southwards in different directions as the Glacial 
jicriod came on. lo tliis theory, which 1 believe originated with the 
American botanist. Dr. Asa Gray, my friend, Mr. 8earles V. Wood, 
junior, has added the bokl but interesting hypothesis that it was 
in high latitudes that deciduous trees were first evolved — that, 
in fact, the habit which so many of our European trees and shrubs 
have of shedding their leaves during winter was originally 
acquired during their e.xposure to the long darkness of the 
Arctic winter. 
In conclusion, I must refer to the last gap in the record with 
Avhich I shall have to-day to trouble you. 
1 ho Eocene bods, the oldest of the Tertiary rocks, rest directly 
on the Chalk, which is of Secondary ago. It seems jirobable, 
so far as marine organisms afford ns a clue, that the period of 
time separating the Eocene beds and the Chalk is greater than 
that which separates the latter from our own era. The difference 
between the forms of animal life which existed in Eocene times 
and those of the present day, great as it is, hoax’s no comparison 
w’hatever to that betw’een those of the Chalk and the Eocene. 
Wo can trace a relationship between the mammalia of the London 
Clay and those of oui’ own times j while, as I have before said, 
some of the mollusca, or shell-fish, are absolutely identical with 
I those now existing. Eut when we pass to Secondary fossils, we 
I find whole families th.at arc not now' represented at all. As, 
for example, among the reptiles, the Ichthyosaurs, the Idesiosaurs,' 
the Jlosasaurs, and those great flying dragons, the Pterodactyles. 
Ihesc all became extinct during this great unrepresented interval 
of time, except it be that the sea-serpent, for whose existence so 
