Changes in the environment notoriously produce changes in certain cases, even in adults. The modifications which may result from the action of unusual agencies on the embryo have been well shown by M. C. Dareste.[28] As has been already remarked, processes of repair take place the more readily the younger the age of the subject. Similarly, it is probable that the action of the environment generally acts more promptly and intensely on the embryo than in the older young. That the same organism will sometimes assume very different forms has been observed by Professor Lankester in the case of _Bacterium rufescens_.[29] [28] See _Archives de Zool. expér._ vol. ii. p. 414 vol. v. p. 174, vol. vi. p. 31; also _Ann. des Sci. Nat. 4 séries, Zoologie_, vol. iii. p. 119, vol. xv. p. 1, vol. xvii. p. 243; and his work _Recherches sur la production artificielle des Monstruositées ou essais de Tératogénie expérimentale_. [29] See _Quarterly Journal of Micros. Soc._, New Series, (1873), vol. xiii. p. 408, and vol. xvi. (1876) p. 27. The effects of changed conditions is often very striking. _Ficus stipulata_ grown on a wall has small, thin leaves, and clings to the surface like a large moss or a miniature ivy. Planted out, it forms a shrub, with large, coarse, leathery leaves. Mr. Wallace has pointed out some of the curious direct effects of external conditions on organisms. He tells us[30] that in the small island of Amboina the butterflies (twelve species, of nine different genera) are larger than those of any of the more considerable islands about it, and that this is an effect probably due to some local influence. In Celebes a whole series of butterflies are not only of a larger size, but have the same peculiar form of wing. The Duke of York’s Island seems, he tells us, to have a tendency to make birds and insects white, or at least pale, and the Philippines to develop metallic colors; while the Moluccas and New Guinea seem to favor blackness and redness in parrots and pigeons. Species of butterflies which in India are provided with a tail to the wing, begin to lose that appendage in the islands, and retain no trace of it on the borders of the Pacific. The Æneas group of papilios never have tails in the equatorial region of the Amazon Valley, but gradually acquire tails, in many cases, as they range towards the northern and southern tropics. Mr. Gould says that birds are more highly colored under a clear atmosphere than in islands or on coasts—a condition which also seems to affect insects, while it is notorious that many shore plants have fleshy leaves. We need but refer to the English oysters mentioned by Costa, which, when transported to the Mediterranean, grew rapidly like the true Mediterranean oyster, and to the twenty different kinds of American trees said by Mr. Meehan to differ in the _same manner_ from their nearest American allies, as well as to the dogs, cats, and rabbits which have been proved to undergo modifications directly