In order that each living creature may be thus furnished, the number of such gemmules in each must be inconceivably great. Mr. Darwin says:[219] "In a highly organized and complex animal, the gemmules thrown off from each different cell or unit throughout the body must be inconceivably numerous and minute. Each unit of each part, as it changes during development--and we know that some insects undergo at least twenty {210} metamorphoses--must throw off its gemmules. All organic beings, moreover, include many dormant gemmules derived from their grandparents and more remote progenitors, but not from all their progenitors. These _almost infinitely numerous_ and minute gemmules must be included in each bud, ovule, spermatozoon, and pollen grain." We have seen also that in certain cases a similar multitude of gemmules must be included also in every considerable part of the whole body of each organism, but where are we to stop? There must be gemmules not only from every organ, but from every component part of such organ, from every subdivision of such component part, and from every cell, thread, or fibre entering into the composition of such subdivision. Moreover, not only from all these, but from each and every successive stage of the evolution and development of such successively more and more elementary parts. At the first glance this new atomic theory has charms from its apparent simplicity, but the attempt thus to follow it out into its ultimate limits and extreme consequences seems to indicate that it is at once insufficient and cumbrous. Mr. Darwin himself is, of course, fully aware that there must be _some_ limit to this aggregation of gemmules. He says:[220] "Excessively minute and numerous as they are believed to be, an infinite number derived, during a long course of modification and descent, from each cell of each progenitor, could not be supported and nourished by the organism." But apart from these matters, which will be more fully considered further on, the hypothesis not only does not appear to account for certain phenomena which, in order to be a valid theory, it ought to account for; but it seems absolutely to conflict with patent and notorious facts. How, for example, does it explain the peculiar reproduction which is {211} found to take place in certain marine worms--certain annelids? [Illustration: AN ANNELID DIVIDING SPONTANEOUSLY. (A new head having been formed towards the hinder end of the body of the parent.)]