At the outset it is desirable to be clear upon certain points touching the history of the subject; the limits within which our discussion is to be confined; the relation in which the present essay stands to the one that I published last year under the title _An Examination of Weismannism_; and several other matters of a preliminary kind. The problems presented by the phenomena of heredity are manifold; but chief among them is the hitherto unanswered question as to the transmission or non-transmission of acquired characters. This is the question to which the present Section will be confined. Although it is usually supposed that this question was first raised by Weismann, such was not the case. Any attentive reader of the successive editions of Darwin's works may perceive that at least from the year 1859 he had the question clearly before his mind; and that during the rest of his life his opinion with regard to it underwent considerable modifications--becoming more and more Lamarckian the longer that he pondered it. But it was not till 1875 that the question was clearly presented to the general public by the independent thought of Mr. Galton, who was led to challenge the Lamarckian factors _in toto_ by way of deduction from his theory of Stirp--the close resemblance of which to Professor Weismann's theory of Germ-plasm has been shown in my _Examination of Weismannism_. Lastly, I was myself led to doubt the Lamarckian factors still further back in the seventies, by having found a reason for questioning the main evidence which Mr. Darwin had adduced in their favour. This doubt was greatly strengthened on reading, in the following year, Mr. Galton's _Theory of Heredity_ just alluded to; and thereupon I commenced a prolonged course of experiments upon the subject, the general nature of which will be stated in future chapters. Presumably many other persons must have entertained similar misgivings touching the inheritance of acquired characters long before the publication of Weismann's first essay upon the subject in 1883. The question as to the inheritance of acquired characters was therefore certainly not first raised by Weismann--although, of course, there is no doubt that it was conceived by him independently, and that he had the great merit of calling general attention to its existence and importance. On the other hand, it cannot be said that he has succeeded in doing very much towards its solution. It is for these reasons that any attempt at dealing with Weismann's fundamental postulate--i.e. that of the non-inheritance of acquired characters--was excluded from my _Examination of Weismannism_. As there stated, he is justified in assuming, for the purposes of his discussion, a negative answer to the question of such inheritance; but evidently the question itself ought not to be included within what we may properly understand by "Weismannism." Weismannism, properly so called, is an elaborate system