On this view of the succession of characters in the life-history of organisms, how shall we explain the undoubted fact that the development of buds hardly ever presents any phenomena corresponding to the embryonic and larval changes? The reason is clearly this, that budding usually occurs after the embryonic stage is past; when the characters of embryonic life have been worked out by the machine. When it takes place at an early stage in embryonic life, as it does in cases of so-called embryonic fission, the product shows, either partly or entirely, phenomena similar to those of embryonic development. The only case known to me in which budding by the adult is accompanied by morphological features similar to those displayed by embryos is furnished by the budding of the medusiform spore-sacs of hydrozoon polyps. But this case is exceptional, for here we have to do with an attempt, which fails, to form a free-swimming organism, the medusa; and the vestiges which appear in the buds are the umbrella-cavity, marginal tentacles, circular canal, etc., of the medusa arrested in development. But the question still remains, are there no cases in which, as implied by the recapitulation theory, variations in any organ are confined to the period in which the organ is functional and do not affect it in the embryonic stages? The teeth of the whalebone whales may be cited as a case in which this is said to occur; but here the teeth are only imperfectly developed in the embryo and are soon absorbed. They have been affected by the change which has produced their disappearance in the adult, but not to complete extinction. Nor are they now likely to be extinguished, for having become exclusively embryonic they are largely protected from the action of natural selection. This consideration brings up a most important aspect of the question, so far as disappearing organs are concerned. Every organ is laid down at a certain period in the embryo and undergoes a certain course of growth until it obtains full functional development. When for any cause reduction begins, it is affected at all stages of its growth, unless it has functional importance in the larva, and in some cases its life is shortened at one or both ends. In cases, as in that of the whale's teeth, in which it entirely disappears in the adult, the latter part of its life is cut off; in others, the beginning of its life may be deferred. This happens, for instance, with the spiracle of many Elasmobranchs, which makes its appearance after the hyobranchial cleft, not before it as it should do, being anterior to it in position, and as it does in the Amniota in which it shows no reduction in size as compared with the other pharyngeal clefts. In those Elasmobranchs in which it is absent in the adult but present in the embryo (e.g. Carcharias) its life is shortened at both ends. Many more instances of organs, of which the beginning and end have been cut off, might be mentioned; e.g.