1032 HISTORICAL GEOLOGY. 



Neuropters, Orthopters, Coleopters, Lepidopters, Hymenopters ; but each was derived, 

 from some early comprehensive forms. 



The results of degeneration afford other series of facts of the highest importance with 

 reference to the origin of species. Some of them, and a few of the principles they illus- 

 trate, are mentioned on pages 717, 931. 



Two systems of evolution. — Lamarck, in his system of Evolution {Phil. 

 Zool., 1809), laid down as one chief cause of variation, the use and disuse of 

 organs or parts, — use causing enlargement, and disuse a dwindling even to 

 disappearance ; and one of his illustrations was drawn from the difference 

 in length of wing of the tame and wild Ducks. He put forth, as other sources 

 of change, the surrounding physical conditions and their often abrupt changes, 

 and referred also, in an imperfect way, to the effect of biological associations, 

 or the influence of the living species of a region on one another. The im- 

 portance of the principle of heredity was also recognized. He added to his 

 system the principle — a tendency upward. . 



Darwin, in his work of 1859, recognized the obvious causes of variation, 

 but claimed that these, and all means of change, derived their eflBciency from 

 action under the principle of "Natural Selection," as indicated in the title 

 of his work. He elucidated the subject of evolution by many illustrations 

 of the effects of breeding and culture under man's care and guidance ; by 

 his study of variation among living plants and animals, wild and domesti- 

 cated, publishing a separate work of great value on Animals and Plants 

 under Domestication; by full illustrations of the laws of heredity; and by 

 new facts, almost a revelation to science, relating to the living environments 

 of species, and the consequent interdependence and interaction of associated 

 kinds in both kingdoms of life. 



According to the principle of natural selection, *' an animal or plant that 

 varies in a manner profitable to itself will have, thereby, a better chance of 

 surviving," and of contributing its qualities and progressive tendency to the 

 race, while others not so favored, or varying disadvantageously, disappear. 

 The favored ones, or the "naturally selected," are one or two, or a few, of a 

 herd, or of a region; and the unfavored ones, fated to disappear because 

 unadaptable, include, theoretically, all the rest. The principle of selective 

 breeding is used in the development of the favored ones ; for these have to 

 be separated from the rest of the herd for success, as in man's selection. 

 The adaptations are to any kind of condition, whether favorable to the 

 highest or to the lowest developments, so that progress under the principle 

 may be upward or downward. The origin of variation is not considered. 

 Everything in nature varies, and changing conditions are always adding to 

 the variations. However produced, the individual that is profited by a 

 variation survives, propagates its characteristics, and becomes the type of a 

 species, while "multitudes" are left behind in the struggle with adverse 

 environments; and thus the new species, in the end, stands widely apart 

 from other species. 



In the expression, "preservation of favored races in the struggle for 



