“Quant à ce qui concerne la prétendue incubation d’œufs d’Infusoires dans l’infusion, il faudrait d’abord prouver l’existence de ces œufs. Les dit-on trop petits pour être aperçus, c’est avouer qu’on ne peut rien savoir de leur existence. * * * Croire que partout où l’on rencontre des Infusoires, ils ont été précédés d’œufs, c’est donc admettre une pure hypothèse, qui n’a d’autre fondement que l’analogie. * * * Si c’est seulement par l’analogie qu’on suppose des œufs chez eux, il faut accorder à ces œufs des propriétés semblables à celles de tous les œufs connus; car ce serait jouer sur les mots que de supposer qu’ils en ont de particulières à eux seuls.”--BURDACH’S _Traité de Physiologie_, Translation by Jourdan, 1837, t. i., p. 22. LONDON: PRINTED BY WILLIAM CLOWES AND SONS, STAMFORD STREET, AND CHARING CROSS. PREFACE. Having been compelled by the results of my investigations on the question of the Origin of Life to arrive at conclusions adverse to generally received opinions, I found that several persons having high authority in matters of science, were little disposed to assent to these views. To a great extent this seemed due to the fact that a distinguished chemist had previously gone over some of the same ground, and had arrived at precisely opposite conclusions. M. Pasteur has been long known as an able and brilliant experimenter, and some of his admirers seem to regard him as an almost equally faultless reasoner. Renewed and prolonged experimentation having tended to demonstrate the truth of my original conclusions, and to convince me of the utter untenability of M. Pasteur’s views, it seemed that the best course to pursue would be, at first, to endeavour to show into what errors of reasoning M. Pasteur had fallen, and also how his conclusions were capable of being reversed by the employment of different experimental materials, and different experimental methods. Then, having presented, in a connected form, evidence which might suffice to shake the faith of all who preserved a right of independent judgment, one might hope to have paved the way for the reception of new views--even though they were adverse to those of M. Pasteur. The present volume contains, indeed, only a fragment of the evidence which will be embodied in a much larger work--now almost completed--relating to the nature and origin of living matter, and in favour of what is termed the physical doctrine of Life.