Part 164. The doctrine of special creation. Linnaeus embodied the belief of his own age and of former times in the famous saying, "We reckon so many species as there were distinct forms created in the beginning." This belief assumes that in somewhat the same way as men have fashioned artificial objects for various uses, so superior beings or one Supreme Being of transcendent wisdom and power, created in the beginning originals of all the different kinds of plants and animals, fitting each to occupy its proper place, and endowing each with the power of perpetuating its like in progeny. In other words, all the living representatives of each species are regarded as the descendants of a first original or pair which was specially created by God, as a distinct and entirely new production, in the most suitable part of the earth, when the world was young; from which place and since which time the species has been distributed over the area that it now occupies. Furthermore, the peculiarities which characterize its living representatives are held to be the same that were impressed in the beginning upon the original progenitors of the species.

The view above outlined is known as the doctrine of fixity of species, or special creation, or as creationism. Since it proved to be satisfactory to the best thinkers of many ages, including many eminent naturalists, it must have afforded a reasonable explanation of numerous facts, and we may be sure therefore that it contains important truth.

A species does seem to be fixed in the sense of having natural limits beyond which unlikeness among its members cannot go. Thus even breeders of domesticated varieties find that they cannot induce more than a certain amount of modification in any one direction. For example, careful experiment has shown that if seeds from a wild carrot be planted in rich soil, and then seeds from the offspring with largest root be similarly planted and tended, and the same process of selection and planting be continued for several generations, there will finally be obtained as large rooted plants as any in cultivation. But sooner or later a size is reached beyond which the root does not increase; and if the most highly cultivated carrot-plants scatter their seed over neglected ground, as too often happens, the plants which are thus allowed to "run wild," as the saying is, soon become indistinguishable from the wild carrots which are pernicious weeds.

Another common experience of breeders is their inability to obtain fertile offspring by mating individuals of different species. It is true that pollen from a white oak may cause the ovules of a post-oak to develop into seeds which may grow into trees perceptibly different from either parent; and such hybrids are occasionally met with in nature. But when carefully observed it is usually found to be true either that hybrids are incapable of bearing offspring, or that such offspring as they have are apt to belong unmistakably to one or the other of the parent species. Many of the so-called hybrids of horticulturists are merely crosses between varieties of the same species and their fertility does not affect the above rule. Here, then, seems to be another definite limit circumscribing a species as if some law of fixity had been imposed upon it from the beginning. Many naturalists have maintained that in case of doubt as to whether two forms are true species or merely varieties, the power to produce perfectly fertile offspring may be used as a final test. Species thus viewed become definite units of classification, which although sometimes difficult to separate in practice are in theory none the less absolute.

Those who have studied plants and animals most closely have always marveled at the ways in which each kind fits its natural environment, that is to say all the conditions under which it naturally lives. Thus among plants the absorption of food materials and the making of food, its storage for future use and its protection from harm, require not only a perfect working together of parts within the organism, but a nice adjustment of all to the surroundings. The structural features and habits of behavior which enable any organism to meet the usual requirements of its life are spoken of as adaptations to its environment.

Creationism views the wonderful adaptations of plants and animals as manifestations of the Creator's wisdom in so forming the progenitor of each species that its descendants shall all fit well into the places they are to occupy. It recognizes kinship only among the individuals of a species. The resemblance among species of the same genus, or among the subdivisions of higher groups in a natural system, it regards as indicating merely similarities of plan which the Creator was pleased to follow, much as an architect uses similar features more or less varied in different parts of a design.