In the summer of 1847 Professor Buckman gathered seed from wild parsnips, and sowed them in the spring of 1848 under changed conditions of life. Most of the plants grown from these seeds were like the wild parsnips, but some of them developed the light-green color and hairless, smooth appearance characteristic of the cultivated plant. The roots also were found to be more fleshy than those of the wild variety. Peas and squashes, when grown in different soils, often show remarkable variations. There is one species of shrimp that inhabits brackish water, and another that lives in water which is much more salt. These crustaceans differ from one another in the character of the spines they bear and in the form of the tail-lobes. They have been regarded as distinct species, and yet either of them can be transformed into the other in the course of a few generations, by gradually altering the saline conditions of the water. For a long while the siredon and amblystoma were regarded as being distinct genera of amphibians. Siredon was looked upon as a permanent gill-breather, while amblystoma passes through a metamorphosis and becomes a permanent lung-breather. It is now known that the former can change into the latter. If there is plenty of water the siredon remains indefinitely a gill-breather and reproduces freely; but when the water dries up it changes into the lung-breathing amblystoma. These two cases illustrate very well the power of environment to modify the development of organic forms. As to “_use_” and “_disuse_”: It can readily be observed that exercise increases the size of muscles; that by steady application the capacity for thinking can be developed; that the oarsman’s constant use of his hands leads to the hardening and thickening of the cuticle; that the arm of the blacksmith and the legs of the mountaineer are much enlarged, etc. When an organ is exercised properly, there is an increased blood supply to it, and, consequently, stimulated nutrition and growth in various parts, such as in the muscular, nervous or other tissues. When an organ is disused there is diminished blood supply, and, consequently, diminished growth and functional capacity. In man it is known that certain activities, such as coal-heaving, shoemaking, etc., produce recognizable effects upon the muscular system, the skeleton, and other parts of the body. The peculiar habits of a tribe, such as tree-climbing among those natives of the interior of New Guinea, who build their houses in the upper limbs of lofty trees, modify the body in ways that are readily recognizable.