president's address. 25 



early and bad less opportunity for transmitting their peculiar 

 qualities to their descendants. It is well known that the off- 

 spring of any organism possess, in general, similar external 

 characters and biochemical properties to their parents. The 

 mechanism by which the resemblances and variations were 

 brought about received little study in the last centur}'. Indeed 

 it was held by most biologists that environment had little in- 

 fluence on the qualities of the different generations of any race, 

 however much it might affect the individual in a particular 

 generation. It was denied emphatically by the Darwinian evo- 

 lutionists that the conditions of the environment could produce 

 new characters in the descendants of any individual. While 

 naturalists, in general, held these views, there were notable dis- 

 sentients from these doctrines. Physicians, who have many 

 occasions for observation in this field, have in general believed 

 that some acquired characters can be transmitted to the offspring. 



The progress of knowledge is showing us that the question of 

 the inheritance of acquired characteis no longer interests this 

 generation in the form in which it attracted the previous genera- 

 tion A wider acquaintance with the qualities of a living thing 

 has led us to have a more comprehensive idea of inheritance. 

 Differences that seemed insurmountable to older generations are 

 no longer differences to us. We can produce an artificial immu- 

 nity to some particular chemical substance, and we find that this 

 immunity can be transmitted permanently to the race. We can 

 cause an animal or plant to acquire new characters, which seem 

 to become fixed characters in succeeding generations. We find 

 that the characters of animals and plants are much more labile 

 than had been supposed, and that it is a comparatively easy 

 matter to engraft some new qualities upon them. There are 

 limits to what can be done, but we have not yet fathomed what 

 can be accomplished. It may be of interest to you to consider 

 how some of these changes can be produced. 



We may take as an example the control of some of the quali 

 ties of micro-organisms which are known to have such intimate 

 relations with the existence of more differentiated animals and 

 plants. The behaviour of yeasts in connection with the conver- 



