“I am also far from asserting that the germ-plasm which, as I hold, is transmitted as the basis of heredity from one generation to another, is absolutely unchangeable or totally uninfluenced by forces residing in the organism within which it is transformed into germ-cells.  I am also compelled to admit it as conceivable that organisms may exert a modifying influence upon their germ-cells, and even that such a process is to a certain extent inevitable.  The nutrition and growth of the individual must exercise some influence upon its germ-cells . . . "

Professor Weismann does indeed go on to say that this influence must be extremely slight, but we do not care how slight the changes produced may be, provided they exist and can be transmitted.  On an earlier page (p. 101) he said in regard to variations generally that we should not expect to find them conspicuous; their frequency would be enough, if they could be accumulated.  The same applies here, if stirring events that occur to the somatic cells can produce any effect at all on offspring.  A very small effect, provided it can be repeated and accumulated in successive generations, is all that even the most exacting Lamarckian will ask for.

Having now made the reader acquainted with the position taken by the leading Charles-Darwinian authorities, I will return to Professor Weismann himself, who declares that the transmission of acquired characters “at first sight certainly seems necessary,” and that “it appears rash to attempt to dispense with its aid.”  He continues:—­

“Many phenomena only appear to be intelligible if we assume the hereditary transmission of such acquired characters as the changes which we ascribe to the use or disuse of particular organs, or to the direct influence of climate.  Furthermore, how can we explain instinct as hereditary habit, unless it has gradually arisen by the accumulation, through heredity, of habits which were practised in succeeding generations?” {277}

I may say in passing that Professor Weismann appears to suppose that the view of instinct just given is part of the Charles-Darwinian system, for on page 389 of his book he says “that many observers had followed Darwin in explaining them [instincts] as inherited habits.”  This was not Mr. Darwin’s own view of the matter.  He wrote:—­

“If we suppose any habitual action to become inherited—­and I think it can be shown that this does sometimes happen—­then the resemblance between what originally was a habit and an instinct becomes so close as not to be distinguished. . . .  But it would be the most serious error to suppose that the greater number of instincts have been acquired by habit in one generation, and then transmitted by inheritance to succeeding generations.  It can be clearly shown that the most wonderful instincts with which we are acquainted, namely, those of the hive-bee and of many ants, could not possibly have been thus acquired.”—­[Origin of Species, ed. 1859, p. 209.]