EVOLUTION 301 



The serum of a given group or type will agglutinate whichever of 

 A or B is absent in the red corpuscles of its own group. Serum 

 of a group individual will agglutinate red cells of A, B, or AB 

 individuals; A serum will agglutinate B or AB corpuscles; B 

 serum will agglutinate A or AB corpuscles; while AB serum will 

 not agglutinate corpuscles of any of the other types. An AB 

 type is a universal recipient; an type, a universal donor. 



Similar blood groups have been discovered in lower mammals, 

 but only in the apes do the groups correspond with those of man; 

 thus adding one more link in the closeness of the relationship 

 between man and the apes. The blood-group characteristic is 

 permanent throughout life and is also inherited. If a mother 

 belongs to the group and her child to the B group, the father 

 could be of B or A B but not or A group. 



Paleontology. — Paleontology deals with the distribution of 

 animals in time. Its material consists of remains of hard parts, 

 such as bone or shell, or imprints of bodies and tracks made in 

 soft mud, later hardened and preserved. A fossilized bone is a 

 bone whose organic constituents have been completely replaced 

 by mineral matter without destroying the original form of the 

 bone. Bones do not survive long if left exposed to the weather 

 on the surface of the ground. Fossilization resulted from the 

 embedding of dead animals in silt and soil at the bottoms of 

 streams, lakes, and oceans, where slow chemical changes trans- 

 formed the harder parts into minerals. It therefore is very sel- 

 dom that the entire bodies of extinct animals are preserved. It 

 is true, of course, that complete skeletons of prehistoric men 

 and of various animals have been found in limestone caverns, 

 and that there are unusual instances where insects have been 

 found in amber and where whole bodies of mammoths have been 

 exposed by the erosion of the covering layers; but these are in the 

 nature of exceptions rather than the rule. The value of paleon- 

 tology, as evidence for evolution, ranks high because fossils 

 definitely prove that animals (and plants, too) have actually 

 changed and that when the fossils are arranged in proper chrono- 

 logical order, they form a more or less progressive series from 

 low to high forms of life. 



The data of paleontology must be interpreted in terms of age 

 as well as in terms of comparative morphology. A paleontologist 

 must be a good comparative anatomist and at the same time 



