Professor Cope, the American paleontologist, was a strong believer in the effect of activity, both upon the individual and upon his descendants. He believed that the insistent beating of the foot of an animal upon the hard soil of the drying Tertiary plateau, had influenced the production of a firmer nail, which spread around the entire end of the toe and made the hoof of the ungulate. He believed that the use 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 wireless 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 subsequently bathes the germ cells of the coming generation 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 favorable variations, is that the process is too inconceivably slow to account for the enormous progress which has been made. The answer has always been that our observation ran back so short a time that we really have no clear idea of how rapid evolution may have been. Again, it has been answered that transitional geological periods, in which there is much change in the physical geography of a country, will produce more rapid evolution than we at present are experiencing.