CONTENTS. xi 



PAGE 



b. Normal Articulations .......... 283 



c. The Physiology of Bone Moulding ..... 285 

 ii. Moulding of the Articulations ........ 287 



a. The Limb Articulations ......... 287 



b. The Forms of Vertebral Centra ...... 302 



iii. Increase of Size Through Use ........ 304 



a. The Proportions of the Limbs and their Segments 305 



b. The Number of the Digits .... ..... 309 



c. The Horns ............. 314 



iv. Mechanical Origin of Dental Types ...... 318 



Preliminary .............. 318 



a. The Origin of Canine Teeth ....... 327 



b. 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 . w; ....... 385 



PART III. THE INHERITANCE OF VARIATION. 



PRELIMINARY ..... ........... 397 



CHAPTER VIII. HEREDITY. 



1. The Question Stated ............ 398 



2. Evidence from Embryology ......... 401 



a. Vertebrata ............. 401 



b. 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 



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



c. Of Characters Due to Disease ....... 430 



