EVOLUTIONARY THEORIES SINCE DARWIN 245 
of the teeth in grinding produced a stronger and 
better molar tooth, and that the offspring shared in 
this advantage. Since Weissmann’s time, however, 
every Lamarckian feels it necessary to suggest some 
method by which the altered body of the parent can 
produce modifications in the germ plasms from which 
the young are to spring. One of our later biologists 
begins to talk of some effect comparable with wire- 
less telegraphy or induced electricity. He believes 
that organs in the adult, not necessarily by direct 
action, but by action from a distance, may alter the 
germ. Of this, there is no proof at present. Others 
have suggested that just as the ductless glands pour 
into the blood chemical substances which materially 
affect the growth and development of other portions 
of the body, so similar enzymes, or other chemical 
substances, may be sent into the blood, which sub- 
sequently bathes the germ cells of the coming gen- 
eration and produces the change. But of this, again, 
there is no proof. We may believe that acquired 
characters are transmitted, but we certainly do not 
have a very clear idea as to how it can be done. 
One of the strongest objections to Darwin’s idea 
of evolution by natural selection of small and favor- 
able variations, is that the process is too inconceiva- 
bly slow to account for the enormous progress which 
has been made. The answer has always been that our 
