Here, as on other occasions, I lie under a heavy disadvantage, for, out of the many striking cases which I have collected, I can give only one or two instances of transitional habits and structures in allied species; and of diversified habits, either constant or occasional, in the same species. And it seems to me that nothing less than a long list of such cases is sufficient to lessen the difficulty in any particular case like that of the bat. WHY NATURE TAKES NO SUDDEN LEAPS. [Origin of Species, page 156.] Finally, then, although in many cases it is most difficult even to conjecture by what transitions organs have arrived at their present state, yet, considering how small the proportion of living and known forms is to the extinct and unknown, I have been astonished how rarely an organ can be named, toward which no transitional grade is known to lead. It certainly is true that new organs, appearing as if created for some special purpose, rarely or never appear in any being--as indeed is shown by that old but somewhat exaggerated canon in natural history of “Natura non facit saltum.” We meet with this admission in the writings of almost every experienced naturalist; or as Milne-Edwards has well expressed it, Nature is prodigal in variety, but niggard in innovation. Why, on the theory of Creation, should there be so much variety and so little real novelty? Why should all the parts and organs of many independent beings, each supposed to have been separately created for its proper place in nature, be so commonly linked together by graduated steps? Why should not Nature take a sudden leap from structure to structure? On the theory of natural selection, we can clearly understand why she should not; for natural selection acts only by taking advantage of slight successive variations; she can never take a great and sudden leap, but must advance by short and sure though slow steps. IMPERFECT CONTRIVANCES OF NATURE ACCOUNTED FOR. [Page 163.] If our reason leads us to admire with enthusiasm a multitude of inimitable contrivances in nature, this same reason tells us, though we may easily err on both sides, that some other contrivances are less perfect. Can we consider the sting of the bee as perfect, which, when used against many kinds of enemies, can not be withdrawn, owing to the backward serratures, and thus inevitably causes the death of the insect by tearing out its viscera?