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, wliile 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 stud}' of the earth's crust found fossil re- 

 mains of many species differing often greatl}' 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 Avere destroA'ed when thej^ were no longer suited 

 to a changed environment, and that new creations adapted 

 to the new conditions then took their place. Thus instead 



