CONTENTS. xi 



r 



PAGE 



b. Normal Articulations 283 



c. The Physiology of Bone Moulding 285 



ii. Moulding of the Articulations 287 



a. The Limb Articulations 287 



/'. The Forms of Vertebral Centra 302 



iii. Increase of Size Through Use 304 



a. The Proportions of the Limbs and their Segments 305 



/'. The Number of the Digits 3^9 



c. The Horns 314 



iv. Mechanical Origin of Dental Types 318 



Preliminary 3^8 



a. The Origin of Canine Teeth 327 



h. The Development of the Incisors 328 



c. The Development of Molars . 331 



d. Origin of the Carnivorous Dentition .... 332 



e. Origin of the Dental Type of the Glires . . . . 345 

 V. Disuse in Mammalia 352 



a. Natatory Limbs 352 



b. Abortion of Phalanges in Ungulata 353 



c. Atrophy of Ulna and Fibula 355 



d. Atrophy of Incisor Teeth 356 



vi. Homoplassy in Mammalia 357 



vii. Origin of the Divisions of Vertebrata 362 



5. Objections to Kinetogenesis 375 



Chapter VII. Natural Selection 385 



PART III. THE INHERITANCE OF VARIATION. 



Preliminary {^^ 



Chapter VIII. Heredity. 



1. The Question Stated 39^ 



2. Evidence from Embryology 401 



a. Vertebrata 401 



/'. Arthropoda 404 



3. Evidence from Paleontology 405 



a. The Impressed Zone of the Nautiloids .... 405 



4. Evidence from Breeding 422 



a. Of Characters Due to Nutrition 423 



h. Of Characters Due to Exercise of Function . . 426 

 c. Of Characters Due to Disease 430 



