VON BALE AXD ELSE OF EMBRYOLOGY. 



I2 5 



Fig. 13. W. His at Sixty-four Years (1831-1004). 



Since physiology is an experimental science, all questions of this 

 nature must be investigated with the help of experiments. Organisms 

 undergoing development have been subjected to changed conditions, 

 and their responses to various forms of stimuli have been noted. In 

 the rise of experimental embryology we have one of the most promising 

 of the recent departures from the older aspects of the subject. The 

 results already attained in this attractive and suggestive field make too 

 long a story to justify its telling in this paper. Eoux, Herbst, Loeb, 

 Morgan, E. B. Wilson and many others have contributed to the growth 

 of this new division of embryology. Good reasons have been adduced 

 for believing that qualitative changes take place in the protoplasm 

 as development proceeds. And a curb has been put upon that ' great 



