Abstract & Overview
After further correspondence the formal invitation was sent me to deliver in Jena the six lectures which appear in printed form in the following pages.It is always a difficult problem to so present new biological discoveries that they will be comprehensible to a mixed public, and yet lose nothing of their scientific value.The reader therefore is requested to exercise a lenient judgment, when he finds that the performance leaves much to be desired.It seemed desirable to consider the first lecture as an introduction which might render it easier for non-biologists to understand the following lectures.The researches quoted are chiefly American.This plan was adopted partly because the author was the American Exchange Professor and partly because he was informed that his audience in Jena would like to hear especially about American discoveries.In the short time at command it was impossible to present the evidence for all that was said, and the reader must be begged to pardon the author if many assertions sound like obiter dicta.vii viii To their Royal Highnesses, the Grand-duke and the Grandduchess of Saxony, the author expresses his thanks for their interest and for the great honor of their presence at one of the lectures.He has pleasure in thanking also their Excellencies, the Ministers of Education of Saxe-Weimar-Eisenach, Altenburg and Meiningen, his Magnificency the Prorektor, the Curator