22 BIOLOaiCAL SOCIETY OF WASHINGTON. 



uals, some in one direction and some in another, and that all 

 except the advantageous ones are immediately lost, while 

 such as tend to increase the chances of survival in the strug- 

 gle for existence are preserved. Nature has thus provided, 

 through this survival of the fittest, for the maintenance of the 

 equilibrium between the organism and the environment, and 

 also for the increase of structural adaptation and vital power, 

 independently both of the effort of the individual to conform 

 more exactly to its surroundings and of the reaction of the 

 organism upon the impinging environment. 



There has never been anj- doubt of the perfect transmissi- 

 bility of these spontaneous modifications, or, as they have been 

 called, fortuitous variations. They belong to the essential na- 

 ture of the organism, and have, as we shall see later on, been 

 ingeniously explained as originating in the very germ itself. 



But with regard to functional modifications, or as they are 

 more commonly called, acquired characters, grave doubts have 

 arisen in the minds of many natiiralists as to whether they are 

 capable of being inherited by the descendants of those in which 

 they have been superinduced. They are in a certain sense for- 

 eign to the organism, external and superficial, and the great 

 question has been how they can succeed in so affecting the 

 reproductive germs of the parents as to reappear in the off- 

 spring. That Darwin believed in the transmission of func- 

 tionally acquired characters is attested not only by many 

 passages in which this belief is expressly stated but by the 

 bringing together by him of more facts in support of it than 

 have been given by all other writers combined either before 

 or since. And although the greater part of his work was 

 naturally directed to the establishment of the hitherto un- 

 known, but as he believed, more important law of selection, 

 nevertheless Darwinism proper must be made broad enough 



