Sachs gives the following account of the fertilization process in _Aristolochia Clematitis_, which he refers to as a conspicuous and peculiar adaptation. In Figure 1 A a group of flowers is shown, and in Figure 1 B and C a single flower is split open to show the interior. In B a small fly has entered, and has brought in upon its back some pollen that has stuck to it in another flower. The fly has entered through the long neck which is beset with hairs which are turned inwards so that the fly can enter but cannot get out. In roaming about, the pollen that is sticking to its back will be rubbed against the stigmatic surface. “As soon as this has taken place the anthers, which have been closed hitherto, dehisc and become freely accessible,” as a result in the change in the stigma and of the collapse of the hairs at the base of the enlargement which has widened. The fly can now crawl under the anthers, and, if it does so, new pollen may stick to its back. At this time the hairs in the throat dry up, and the fly can leave its prison house, Figure 1 C. If the fly now enters another flower this is fertilized by repeating the process. The unfertilized flowers stand erect with widely open mouths. As soon as they have been fertilized they bend down, as seen in Figure 1 A, and at the same time the terminal flap bends over the open mouth of the throat, “stopping the entrance to the flies, which have now nothing more to do here.” Adjustments of the Individual to Changes in the Environment The most familiar cases of adjustments of the individual to the environment are those that we recognize in our own bodies. After violent exercise we breathe more rapidly, and take deeper inspirations. Since during exercise our blood loses more oxygen and takes in more carbon dioxide from the muscles, it is clear that one result of more rapid breathing is to get more oxygen into the blood and more carbon dioxide out of it. The process of sweating, that also follows exercise, may be also looked upon as an adaptive process, since by evaporation the skin is kept cooler, and, in consequence, the blood, which at this time flows in larger quantities to the skin, is cooled also. More permanent adaptive changes than these also take place as the result of prolonged use of certain parts. If the muscles work against powerful resistance, they become larger after several days or weeks, and are capable of doing more work than at first. Conversely, when any group of muscles is not used, it becomes smaller than the normal and capable of doing less work. It would be a nice point to decide whether this latter change is also an adaptation. If so it is one in a somewhat different sense from that usually employed. The result is of no direct advantage to the animal, except possibly in saving a certain amount of food, but since the same change will take place when an abundance of food is consumed, the result is, under these conditions, of no use.