ANNIVERSARY ADDRESS OF THE PRESIDENT. li 
Carnwora, and Cetacea. But the Chiroptera are extreme modifi- 
cations of the Jnsectivora, just as the Cetacea are extreme modifica- 
tions of the Carnivorous type; and therefore it is to my mind 
incredible that monodelphous Jnsectivora and Carnivora should not 
have been abundantly developed, along with Ungulata, in the Meso- 
zoic epoch. But if this be the case, how much further back must 
we go to find the common stock of the monodelphous Mammalia? 
As to the Didelphia, if we may trust the evidence which seems to 
be afforded by their very scanty remains, a Hypsiprymnoid form 
existed at the epoch of the Trias, side by side with a carnivorous 
form. At the epoch of the Trias, therefore, the Marsupialia must 
have already existed long enough to have become differentiated 
into carnivorous and herbivorous forms. But the Monotremata are 
lower forms than the Didelphia, which last are intercalary between 
the Ornithodelphia and the Monodelphia. To what point of the 
Paleozoic epoch, then, must we, upon any rational estimate, relegate 
the origin of the Monotremata? 
The investigation of the occurrence of the classes and of the 
orders of the Sauropsida in time points in exactly the same direc- 
tion. If, as there is great reason to believe, true Birds existed in the 
Triassic epoch, the ornithoscelidous forms by which Reptiles passed 
into Birds must have preceded them. In fact there is, even at 
present, considerable ground for suspecting the existence of Dino- 
sauria in the Permian formations; but, in that case, lizards must be 
of still earlier date. And if the very small differences which are 
observable between the Crocodilia of the older Mesozoic formations 
and those of the present day furnish any sort of approximation 
towords an estimate of the average rate of change among the Sau- 
ropsida, it is almost appalling to reflect how far back in Paleozoic 
times we must go before we can hope to arrive at that common stock 
from which the Crocodilia, Lacertilia, Ornithoscelida, and Plesio- 
sauria, which had attained so great a development in the Triassic 
epoch, must have been derived. 
The Amphibia and Pisces tell the same story. There is not a 
single class of yertebrated animals which, when it first appears, is 
represented by analogues of the lowest known members of the same 
class. Therefore, if there is any truth in the doctrine of evolution, 
every class must be vastly older than the first record of its appear- 
ance upon the surface of the globe. But if considerations of this 
kind compel us to place the origin of vertebrated animals at a period 
sufficiently distant from the Upper Silurian, in which the first Elas- 
mobranchs and Ganoids occur, to allow of the evolution of such fishes 
as these from a Vertebrate as simple as the Amphiowus, I can only 
repeat that it is appalling to speculate upon the extent to which 
that origin must have preceded the epoch of the first recorded 
appearance of vertebrate life. 
Such is the further commentary which I have to offer upon the 
statement of the chief results of paleontology which I formerly ven- 
tured to lay before you. 
