40 BIOLOGICAL SOCIETY OF WASHINGTON. 



indefinite series of ancestors, and containing representatives of 

 every part of the parent organism, proceed to reproduce a new 

 creature on the hereditary type of the parents with the modifi 

 cations due to the commingling of many ancestral types. 



Without dwelling longer upon these ultimate processes 

 which constitute the premises of Weismann's argument, I will 

 now proceed to state his conclusion. It is simply that he is 

 utterly unable to see how the somatic cells of an adult indi 

 vidual can react upon or in any way affect its reproductive 

 cells. If it cannot, the transmission through either parent to 

 its offspring of any peculiarity acquired since the embryo of the 

 parent began to form is impossible. Firmly believing in the 

 truth of his theory he stoutly insists that no such thing can 

 take place. Of course it needs to be clearly understood what 

 he means by acquired characters, and here, it is claimed lies 

 the chief point in dispute between the Neo-Darwinians and the 

 Neo-Lamarckians. The former contend that the latter class as 

 acquired characters those which are simply due to natural 

 selection. It will therefore be profitable to dwell a moment 

 upon this point. 



"The tendencies of heredity ", says Weismann, " of which 

 the germ -plasm is the bearer, depend upon this very molecular 

 structure, and hence only those characters can be transmitted 

 through successive generations which have been previously in 

 herited, viz. , those characters which were potentially contained 

 in the structure of the germ-plasm. It also follows that those 

 other characters which have been acquired by the influence of 

 special external conditions, during the lifetime of the parent, 

 cannot be transmitted at all " (p. 267). ' ' It is only by suppos 

 ing that these changes arose from molecular alterations in the 

 reproductive cell that we can understand how the reproductive 

 cells of the next generation can originate the same changes in 



