PALEONTOLOGY AND GENETICS 



ters. It may be stated, however, that it has been demonstrated that the 

 genes (hereditary determiners) are quite constant, and are inherited on 

 a statistically predictable basis. They tend, therefore, to keep species con- 

 stant. However the genes are capable of undergoing a change (mutation), 

 so that the trait determined is different from the original and is just as 

 stable. Hence mutation forms the basis of hereditary variability, which is 

 the raw material of evolution. 



REFERENCES 



Aldhich, L. T., 1956. "Measurement of Radioactive Ages of Rocks," Science, 123, 

 871-875. A brief description of the methods, witli some of the recent results. 



Darwin, C. R., 1859. "Origin of Species," Chapter X, "On the Imperfections of the 

 Geological Record." After a century, this is still the finest treatment of the subject. 



Gregory, W. K., 1951. "Evolution Emerging," Vols. I and II, The Macmillan Co., New 

 York, N.Y. An exhaustive presentation of the viewpoint of a paleontologist at the end 

 of a long career. 



Moore, R. C, 1958. "Introduction to Historical Geology," 2nd Ed., McGraw-Hill Book 

 Co., New York, N.Y. Paleontologv is well presented here. 



RoMER, Alfred S., 1945. "Vertebrate Paleontology," 2nd Ed., University of Chicago 

 Press. An excellent treatment of the vertebrates. 



Stirton, R. a., 1959. "Time, Life, and Man," John Wiley & Sons, New York, N.Y. 

 A well illustrated, nontechnical introduction to paleontology. 



White, E. I., 1946. "Jamoijtius kerwoodi, a new Chordate from the Silurian of Lanark- 

 shire," Geological Magazine, 83, 89. The original description of this interesting and 

 controversial fossil. 



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