PREFACE. ENGAGED in constant efforts to trace and clear up the history of animal reproduction, as far as this is permitted to human discernment, I have been guided to a phnomenon in Insect life which had for a long time remained obscure to me,-I refer to the power of reproduction of some female Insects which remain unfecundated, as this not only appeared to be a great mystery, but even a fact never yet firmly established, and therefore still doubtful. I always found this so-called Lucinu sine concubitu treated by physiologists as a sort of curiosity the same examples from Insect-life, derived from the older observers, mere constantly referred to as vouchers. The question, whether the fact referred to was supported upon a firm basis, remained at the same time altogether unnoticed. As every kind of statement with regard to Lucina sine concubitu has received with so little caution and without suspicion, new observations were added to the older defective notices of this kind but these, in the same way, appeared inadmissible as soon as they were carefully analysed. Since the process of the fecundation of the egg has become much better understood by the recent discoveries of Newport, Iceber, Bischoff, Leuclcart, Meissner, and Bruch, one was compelled to say, that all the cases of Lucina sine conczbitu observed in former or modern days might be founded upon delusion or error, because up to this time the knowledge of the conditions under which fecundation takes place was still extremely imperfect.....