426 A CENTURY OF SCIENCE 



the part of some of our biologists engaged in experimen- 

 tal work to disparage the studies of the systematists. It 

 must be granted, however, that both lines of work are 

 essential to the sound development of zoological science, 

 for experimental investigations in which the accurate 

 diagnosis of species is ignored always result in confusion. 



Ecology. The marvelous modifications in structure 

 and instincts by which the various animals are adapted 

 to their surroundings now forms a special topic in biolog- 

 ical research and one of the most fascinating. The adap- 

 tations in habitat, time, behavior, appearance and even 

 in structure are found capable of a certain individual 

 modification when studied experimentally. 



Zoogeography. Closely associated with systematic 

 zoology, and indeed a part of the subject in its broader 

 sense, is the study of the geographical distribution of 

 animal species and larger groups. 



Paleontology. The geological succession of organisms 

 embraces a field where zoologist and geologist meet. 

 The wonderful progress made by American investiga- 

 tors is well described in the preceding chapters on His- 

 torical Geology and Vertebrate Paleontology. 



Biometry. 



Since Darwin's theory of evolution postulated the 

 origin of new species by means of natural selection, it 

 was obviously necessary in order to apply a critical test 

 to determine the precise limits of a species. It was, 

 therefore, proposed to subject a given species to a strict 

 examination by the application of statistical methods to 

 determine the range of variation of its members and the 

 extent to which the species intergrades with others. 

 Other problems, particularly those concerning heredity, 

 were treated in similar manner. This branch of biolog- 

 ical science was particularly developed by the English 

 School, led by Sir Francis Galton, followed by Karl 

 Pearson and William Bate son. 



In America the methods of biometry have been utilized 

 extensively by Charles B. Davenport, Eaymond Pearl, H. 

 S. Jennings and others in the solution of problems in 

 genetics and evolution. Their work shows the great 



