48 BIOLOGICAL SOCIETY OF WASHINGTON. 



state of the organism in which they lie hid. . . It is even pos- 

 sible that the effects of these influences may be more special- 

 ized ; that is to say, that they may act only upon certain parts 

 of the germ-cells " (pp. 103-104). But he seems to see a great 

 difference between this and the transmission of characters ac- 

 quired in certain special organs to the sa'me organs of the off- 

 spring. This would probably be clear only to an embryologist. 

 One of the most suggestive thoughts in his whole philosophy is 

 that of the total dissimilarit}^ between the germ and the devel- 

 oped organism which is to result from it. He maintains with 

 every semblance of truth that there can be nothing in common 

 l^etween them except the fact that the molecular structure of 

 the germ is such that if allowed to develop it will produce a 

 being similar to the one from which it sprung. This principle 

 seems to be peculiarly applicable to the subtle influences which 

 effect heredity, and without appealing to anything occult or 

 abandoning the strictly casual and mechanical theory of hered- 

 ity, it may be submitted whether we know enough about it as 

 yet to assert that influences affecting the parental organism, 

 even any of its organs, may not react specifically and in kind 

 upon the germ and set up molecular tendencies in the same 

 direction. This may be said quite independently of any at- 

 tempt to explain precisely how it can do so, as the theory of 

 pangenesis claims to do. 



If the germ-plasms vary within the body of either parent be- 

 fore they are brought together that variation must be due to 

 influences acting upon them in the animal body. All this 

 Weismann admits, but he denies that the changes which he 

 admits to take place in the individual as the result of changes 

 in the environment and subsequent changes in the habits and 

 activities of the creature can be regarded as among the causes 

 which produce changes in the germ-plasm. Is this logical or 



