432 KINSHIP AND ADAPTATION 
tionists supposed to exist. Naturalists of eminence frequently © 
differ widely as to the number of species into which the forms 
of a given genus should be divided. It often happens that 
one botanist recognizes several times as many species as 
another admits in the same genus. For example, one says 
there are but thirty species of rose, while another makes the 
number three hundred. Then too, the test of fertility in the. 
offspring proved in practice to be disappointing. It was 
found that certain forms which no one had ever doubted to 
be distinct species did sometimes produce fertile hybrids; 
while, on the other hand, undoubted varieties hybridized 
imperfectly. Therefore, it was urged, if no one can tell which 
forms have come from one original ancestor and which from 
another, what is the use of supposing, as the creationists do, 
that resemblance between species means something entirely 
different from resemblance between varieties? 
Another weak point in creationism was its underlying idea 
that the plants and animals of to-day are of the same forms 
which have lived upon the earth from the earliest times. 
Geologists in their study of the earth’s crust found ‘fossil re- 
mains of many species differing often greatly from any now 
living. As a rule the more ancient the forms, the less they 
are like those of modern times. That is to say, fossils show 
that old forms have continually given place to new ones dur- 
ing the course of geologic ages. Furthermore, contrary to 
the original supposition of creationism, that conditions upon 
the earth’s surface have remained substantially the same 
since the appearance of life, the rocks show that extreme 
changes of climate have taken place. For example, scored 
ledges, transported boulders, and other evidences of glacial — 
action prove that during the last geological period, ‘the 
region from Pennyslvania northward was buried under a 
vast sheet of ice much as Greenland is to-day, while long 
before that time the coal plants of Pennsylvania flourished 
in a climate of subtropical warmth. To these geological 
facts creationists adjusted their belief by supposing that the 
older species were destroyed when they were no longer suited 
to a changed environment, and that new creations adapted 
to the new conditions then took their place. Thus instead 
