Produced by Charlene Taylor, Bryan Ness, Matthew Wheaton and the Online Distributed Proofreading Team at http://www.pgdp.net (This file was produced from images generously made available by The Internet Archive) ON THE VARIATION OF SPECIES WITH ESPECIAL REFERENCE TO THE INSECTA; FOLLOWED BY AN INQUIRY INTO THE NATURE OF GENERA. BY T. VERNON WOLLASTON, M.A., F.L.S. "No compound of this earthly ball Is like another, all in all." TENNYSON. LONDON: JOHN VAN VOORST, PATERNOSTER ROW. 1856. "I do not enter so far into the province of the logicians as to take notice of the difference there is between the _analytic_ and _synthetic_ methods of coming at truth, or proving it;--whether it is better to begin the disquisition from the subject, or from the attribute. If by the use of _proper media_ anything can be showed to be, or not to be, I care not from what term the demonstration or argument takes its rise. Either way propositions may beget their like, and more truth be brought into the world."--_Religion of Nature Delineated_, p. 45 (A.D. 1722). PRINTED BY TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET. TO CHARLES DARWIN, ESQ., M.A., V.P.R.S., Whose researches, in various parts of the world, have added so much to our knowledge of Zoological geography, this short Treatise is dedicated. PREFACE. To make a dry subject entertaining, is impossible; but to render it, at any rate, readable, has been my endeavour in the following pages. How far I have succeeded in the experiment, it is not for me to decide. It having been suggested, by several of my friends, that it might be desirable to bring together into a small compass some of the evidence on Insect variation (with reference to external disturbing causes) which my researches in the Madeira Islands have supplied me with, I have been encouraged to do so: and I have added numerous conclusions from other data also, which have from time to time fallen in my way,--so as to confer on the volume a more practical interest, for the general naturalist. One of my main objects, however, has been to call attention to the fact, that the Annulosa have not been hitherto sufficiently considered, in the great questions arising out of the distribution of animals and plants; hoping that, by so doing, some few of our British entomologists, who have not looked into this branch of their science, may be induced to enlist themselves in the cause of Insect geography. If such a result be brought about; or if I be fortunate enough to open for discussion any of the topics which have been touched upon, and so lead to a more perfect solution of the problems which I have attempted to explain, I shall consider myself more than repaid. 10 Hereford Street, Park Lane, London. May 10th, 1856. CONTENTS. CHAPTER I. Introductory Remarks