300 KANSAS CITY REVIEW OF SCIENCE. 
period in the world's history. That such has been the case is rendered certain 
by the variations of form and other characters which are so commonly met with 
in animals and plants, whose descent we can observe. To believe that species 
were originally created distinct requires that those varieties should also have 
been distinctly created, which we know nol to have been the case. While we 
cannot observe these changes in fossil species, we frequently find variations in . 
them of a character identical with those seen in living species : and we can prop- 
erly infer that the origin of these varieties has been the same in both cases. The 
late discoveries of palaeontology have disclosed a general system of relations of 
the extinct species, entirely accordant with the process of solution from simple to 
more complex lorms of life. The constant discovery of new forms of life and 
even of new populations of animals and plants, demonstrates the imperfection of 
the geological record, and holds out the promise that we will sometime have a 
completed genealogy of all existing animals, including man. 
The speaker referred to the two great phenomena of constancy and varia- 
tion, which meet the student of biology upon every hand, and dwelt at some 
length particularly upon the subject of variation. After giving some instances of 
variability as observed in certain birds and animals, he said : 
The amount or degree of difference is a graduated quantity, and passes 
insensibly from the lesser to the greater; that is from the varietal to the specific. 
Besides we find related species constant in one part of the world, to be variable 
in another; also that individuals can be distinguished into species in two regions 
each taken separately, but, when all are compared together, the definitions of 
species vanish. These facts confirm us in the lawfulness of the general induction 
that all species, no matter how constant they may appear to us now, have been 
at some other time and place as variable as the most variable ones known to us. 
Moreover, to suppose that new elements of form, color, etc., can be introduced 
by the operation of laws of development in one set of organisms and not in 
another, is to violate the very foundation of all practical and instructive reason- 
ing. It is also equally certain that the structural characters in which we have 
genera, families and orders are variable in some parts of the system. This, then, 
is the primary evidence of the descent of existing types from pre-existent ones. 
Taken by itself, this evidence is not conclusive, but in connection with that 
derived from the observation of living specimens, is cumulative to a degree which 
satisfies the mind as to the general fact of evolution, and already explains much 
of its mode and manner. 
The speaker went on to show that although the geological record of the 
fossil mammalia is imperfect, it has become unsafe to assert that connecting forms 
have not been found, and still more unsafe to assert that they will not be 
found. 
As to whether any intermediate form connecting man with the lower ani- 
'mals has yet been found we cannot speak with certainty. The earliest preserved 
human skeletons often represent well developed men, while others are less well 
eveloped, as, for instance, the jaw found at Nanlette, Belgium, which is very 
