The following cases show more clearly the immediate effect of the environment: “Many animals, when transferred to warm climates, lose their wool, or their hairy covering is much reduced. In some parts of the warmer regions of the earth, sheep have no wool, but merely hairs like those of dogs. Similarly, as Roulin notices, poultry have, in Columbia, lost their feathers, and while the young are at first covered with a black and delicate down, they lose it in great part as they grow, and the adult fowls nearly realize Plato’s realistic description of man—a biped without feathers. Conversely, many animals when transferred from warm to cold climates acquire a thicker covering; dogs and horses, for instance, becoming covered with wool.” A number of kinds of snails that were supposed to belong to different species have been found, on further examination, to be only varieties due to the environment. “Locard has discovered through experiments that _L. turgida_ and _elophila_ are mere varieties—due to environment—of the common _Lymnæa stagnalis_.” He says, “These are not new species, but merely common aspects of a common type, which is capable of modification and of adaptation according to the nature of the media in which it has to live.” It has also been shown by Bateson that similar changes occur in _Cardium edule_, and other lamellibranchs are known to vary according to the nature of the water in which they live. In regard to plants, the influence of the environment has long been known to produce an effect on the form, color, etc., of the individuals. “The common dandelion (_Taraxacum densleonis_) has in dry soil leaves which are much more irregular and incised, while they are hardly dentate in marshy stations, where it is called _Taraxacum palustre_. “Individuals growing near the seashore differ markedly from those growing far inland. Similarly, species such as some Ranunculi, which can live under water as well as in air, exhibit marked differences when considered in their different stations, as is well known to all. These differences may be important enough to induce botanists to believe in the existence of two different species when there is only one.”