PRESIDENTIAL ADDRESS. 25 



all the investigators who from the first to last have taken this 

 view, or some modified form of it, and I shall be content to 

 name among Germans Du Boise Reymond, Pfliiger, His, and 

 Weismann, and among Englishmen Galton, Wallace, and Ray 

 Lankester ; while what I shall have time to say relative to 

 the nature of the objections raised by these authors will be 

 chiefly confined, for the present, to the views of Galton and 

 Weismann. 



THEORIES OF HEREDITY. 



It must, however, be premised that inasmuch as the objec- 

 tions raised against the doctrine of the transmission of ac- 

 quired characters are based upon the difficulties encountered 

 in attempting to explain how such characters can impress 

 themselves upon the germ, all those who have doubted or de- 

 nied such transmission have approached the subject from the 

 side of embryology, which makes their arguments difficult to 

 explain to biologists in general and still more so to the general 

 public. The laws and processes of heredity are still in the 

 stage of mystery, and their mysterious character has led to 

 many erroneous beliefs and popular superstitions. It is a sig- 

 nificant fact that all the mysteries that have been thus far 

 cleared up by science — astronomical, physical and chemical 

 mysteries — have been shown to be the expressions of previ- 

 ously unknown laws of matter and force, and to rest upon a 

 purely material and mechanical basis. The chief obstacle to 

 their comprehension has been the minuteness of the material 

 elements in action — a minuteness far beyond the capacity of 

 the most powerful artificial aids to the senses — so that their 

 secrets have had to be wrung from them by ingenious and 

 multiplied experiments upon their effects. Now, the ultimate 



