“Qui enim Autorum verba legentes, rerum ipsarum imagines (eorum verbis comprehensa) sensibus propriis non abstrahunt, hi non veras Ideas, sed falsa Idola et phantasmata inania mente concipiunt . . . . . . .
“Insusurro itaque in aurem tibi (amice Lector!) ut quæcunque à nobis in hisce . . . . exercitationibus tractabuntur, ad exactam experientiæ trutinam pensites: fidemque iis non aliter adhibeas, nisi quatenus eadem indubitato sensuum testimonio firmissime stabiliri deprehenderis.”—HARVEY. Exercitationes de Generatione. Præfatio.
“La seule et vraie Science est la connaissance des faits: l’esprit ne peut pas y suppléer et les faits sont dans les sciences ce qu’est l’expérience dans la vie civile.”
“Le seul et le vrai moyen d’avancer la science est de travailler à la description et à l’histoire des differentes choses qui en font l’objet.”—BUFFON. Discours de la manière d’étudier et de traiter l’Histoire Naturelle.
“Ebenso hat mich auch die genäuere Untersuchung unsers Krebses gelehret, dass, so gemein und geringschätzig solcher auch den meisten zu seyn scheinet, sich an selbigem doch so viel Wunderbares findet, dass es auch den grossten Naturforscher schwer fallen sollte solches ailes deutlich zu beschreiben.”—ROESEL V. ROSENHOF. Insecten Belustigungen.—“Der Flusskrebs hiesiges Landes mit seinen merkwurdigen Eigenschaften.”
PREFACE.
In writing this book about Crayfishes it has not been my intention to compose a zoological monograph on that group of animals. Such a work, to be worthy of the name, would require the devotion of years of patient study to a mass of materials collected from many parts of the world. Nor has it been my ambition to write a treatise upon our English crayfish, which should in any way provoke comparison with the memorable labours of Lyonet, Bojanus, or Strauss Durckheim, upon the willow caterpillar, the tortoise, and the cockchafer. What I have had in view is a much humbler, though perhaps, in the present state of science, not less useful object. I have desired, in fact, to show how the careful study of one of the commonest and most insignificant of animals, leads us, step by step, from every-day knowledge to the widest generalizations and the most difficult problems of zoology; and, indeed, of biological science in general.