274 AN INTRODUCTION TO ZOOLOGY 



their original form, though they continue to exert an important 

 influence upon many lines of research. 



Some of the more recent workers in this field are Mendel, 

 Weismann, and de Vries. Gregor Mendel (1822-1884) was an 

 Austrian monk whose results from a study of the crossing of 

 different kinds of peas and other plants have given us one of the 

 few laws of heredity. An account of his work will be found in 

 Chapter XIV (p. 289). August Weismann (born 1834) is an 

 ardent supporter of Darwinism. He is the foremost living evo- 

 lutionary zoologist. Hugo de Vries has recently brought forth 

 a work entitled Die Mutationstheorie, published in 1901, which 

 combats Darwin's theories of the origin of species, and offers 

 in its stead the " mutation theory," a discussion of which is 

 reserved for the next chapter. 



g. Zoology of To-day 



As the facts of zoological sciences have increased in number, 

 the fields of work have become more numerous and narrower, and 

 investigations are now carried on by more improved methods and 

 in greater detail than ever before. Morphological studies are 

 being supplemented by experimental investigations in embryol- 

 ogy, regeneration, heredity, evolution, and other sciences. Ani- 

 mal behavior is one of the most favored subjects of research, and 

 is rapidly leading psychologists to a better understanding of the 

 animal mind. 



Zoology at the present time presents a rich field for original 

 research. Many of the apparently simple " laws " have been 

 found on close examination to be really very complex. All lines 

 of experimental work offer large rewards for the student and open 

 up for him a countless number of fascinating problems. 



