A CENTURY OF ZOOLOGY IN AMERICA 415 



Period of Experimental Biology, since 189O. 



Zoological studies remained in large measure observa- 

 tional and comparative until about 1890 when the experi- 

 mental methods of Roux, Driesch and others came into 

 prominence. Interest then turned from the accumulation 

 of facts to an analysis of the underlying principles of 

 biological phenomena. The question now was not so 

 much what the organism does as how it does what is 

 observed, and this question could be answered only by 

 the experimental control of the conditions. These exper- 

 imental studies met with such remarkable success that in 

 a few years the older morphological studies were largely 

 abandoned, the Morphological Society changed its name 

 to the Society of Zoologists, and in 1904 the Journal of 

 Experimental Zoology was established. The experimen- 

 tal methods were applied to all branches of biological 

 science, and while it must be freely admitted that little 

 progress has been made toward an understanding of the 

 ultimate causes which underlie biological phenomena, a 

 great advance has been made in the elucidation of the 

 general principles involved. 



Experimental embryology, histology, regeneration, 

 comparative physiology, neurology, cytology, and hered- 

 ity have in recent years successfully adopted an experi- 

 mental aspect and have made significant ^ progress 

 thereby. Biology has now taken its place beside chem- 

 istry and physics as an experimental science. 



The latest great advance in biology has been in the field 

 of heredity. The rediscovery of the Mendelian principles 

 of heredity in 1900 brought to light the most important 

 generalization in biology in recent times. The new 

 science of genetics is essentially the experimental study 

 of heredity. /MI.* 



We are at the moment in the midst of an effort^ 

 establish in biology a few relatively simple laws by using 

 for the purpose the vast accumulations of observational 

 data gathered in past years, supplemented by such exper- 

 imental data as have been provided by these more rec. 

 investigations. Such hypotheses as have been formu- 

 lated are for the most part only tentatively held, for their 



