Chapter III. _The Atom._ In the text I have quoted the great masters,

Ehrenberg, Dujardin, Pouchet, Heterogenie. In the end spontaneous generation will conquer.

Chapters IV., V., VI., &c. Throughout this book, in ascending from inferior to superior life, I have taken for my guiding thread in the great labyrinth, the hypothesis of Metamorphosis but without serious intention of constructing a _chain of beings_. The idea of ascending Metamorphosis is natural to the mind, and is, in some sort, irresistibly imposed upon us. Cuvier himself, at the close of his Introduction to his _Poissons_, confesses that if that theory has no Historical value it _has a logical value_. On the _Sponge_, see Paul Gervais Dict. d'Orb. V. 375; Grant in Chenn, 307, &c. On Polypes, Corals, and Madrepores (Chapters 4 and 5) besides Forster, Peron and Dawin consult Quoy and Gaimard; Lamouroux, _Polypes Flexibles_; Milne Edwards, Polypes and Ascidies of the Channel, &c. On the Calcaire, see the two Geologies of Lyell.