26 IOWA ACADEMY OF SCIENCES. 



PRESIDENTIAL ADDRESS. 



SOME PROBLEMS OF HEREDITY AND EVOLUTION. 



BY H. E. SUMMERS. 



Of all biological problems none is of more importance 

 and interest to the mass of mankind than that dealing 

 with the laws of evolution. To the biologist, of course, 

 these laws are of prime importance, as expressing the ulti- 

 mate result of all life processes. But I refer here rather 

 to the widespread interest among all classes of educated 

 people, due, I believe, to a feeling that as our human civili- 

 zation is advancing in conformity with these laws, a fuller 

 knowledge of them might enable us the better to guide 

 and control our progress in the future. 



Underlying the laws of evolution, however, we have the 

 laws of heredity. A knowledge of the latter is a neces- 

 sary prerequisite for a full understanding of the former. 

 Problems of heredity and evolution are so interwoven that 

 it is impossible entirely to separate them. Indeed, proba- 

 bly the most important question to the student of evolu- 

 tion to-day, that as to the transmissibility of acquii'ed 

 characters, is a question of heredity. It is to a review of 

 .some of the problems of heredity^ therefore, that I shall 

 mainly devote this paper. 



Let us have clearly before us the meaning of the term 

 heredity. 



1. Every individual organism develops from a germ (in 

 the animal the ovum or egg), of relatively small size 

 and apparently simple structure, which in the great 

 majority of cases has no vital connection with its parent 

 after the beginning of its development. 



