ILLUSTRATIONS xxxi 



FIG. PAGE 



112. The tree shrew, Tnpaia 235 



113. Primitive types of monotreme and marsupial ....... 235 



114. Ancestral tree of the mammals 236 



115. Adaptive radiation of the mammals 239 



116. Alternating adaptation in the kangaroo marsupials 243 



117. Evolution of proportion. Okapi and giraffe 24S 



118. Brachydactyly and dolichodactyly 249 



119. Result of removing the thyroid and parathyroid glands . . . . 250 



120. Result of removing the pituitary body 251 



121. Main subdivisions of geologic time 256 



122. Map — North Polar theory of the distribution of mammals . . . 257 



123. Scene in western Wyoming in Middle Eocene times 258 



124. Two stages in the early evolution of the ungulates 259 



125. A primitive whale from the Eocene of Alabama 260 



126. Map — North America in Upper Oligocene time 262 



127. Two stages in the evolution of the titanotheres 263 



128. Evolution of the horn in the titanotheres 264 



129. Horses of Oligocene time 266 



130. Stages in the evolution of the horse 267 



131. Epitome of proportion evolution in the Proboscidea 269 



132. Map — the ice-fields of the fourth glaciation 270 



133. Groups of reindeer and woolly mammoth 271 



134. Glacial environment of the woolly rhinoceros 272 



135- Pygmies and plainsmen of New Guinea 273 



TABLES 



I. Distribution of the chemical elements t,^ 



II. Functions of the life elements (0 face 67 



