The Primary Factors of Organic Evolution

acquired characters adult Amblypoda American Naturalist anagenetic ancestors animals appear articulations Artiodactyla Batrachia become body bones canine Carnivora carpus cause cells Cetacea changes coiling color Condylarthra condyle Cope Creodonta crests cusps cyrtoceran degeneracy dentition digits Diplarthra direction disuse dorsal effect elbow-joint embryo energy Eocene evidence evolution existing external fact feet fins fishes forms genera genus germ-plasma Glires groove growth gyroceran humerus Hyatt impressed zone incisors increase inferior molars inherited kinetogenesis larvæ later limbs lower jaw Mammalia mammals mastication mechanical ment modifications movements muscles muscular natural selection nautilian nautiloids observed organic origin Osceola doliata paleontology Perissodactyla Phenacodus phylogeny plantigrade plants posterior premolars present primitive probably produced protoplasm reduced represented reproduction Reptilia result Ryder segments shell side Sirenia skeleton skull soma species spots stage stimuli strain structure superior molars surface tion tissue tritubercular ulna Ungulata variations vertebral vertebral column Vertebrata whorl