382 THE PHILOSOPHY OF BIOLOGY 



301 ; a series of phases in a transforming system, 298 ; a logical hypo- 

 thesis, 214 ; parallel processes in, 234 ; geological time inadequate for 

 237 ; side paths in, 262 ; mechanistic hypotheses inadequate, 237 ; 

 cosmic, 214, 297, 314 ; of the crust of the earth, 264. 



Excretory products, 269. 



Exoskeleton, 276. 



Exothermic reactions, 86. 



Experience and duration, 156. 



Experimental biology proves evolution, 246. 



Explosive reactions, loi. 



Extension in space, 18. 



Extinct groups, 263. 



Fats, digestion of, 93. 



Fecundity of animals, 179, 239. 



Ferments, 92. 



Fertilisation (in reproduction), 176. 



Finalism, 216. 



Fishes, distribution of, 261. 



Fluctuating variations, 200. 



Food-stuffs, absorption of, 89. 



Force, 354. 



Form, accidental and essential, 167, 353 ; 



geological, 168 ; crystalline, 168. 

 Frequency distributions, 22, 187, 350. 

 Frog, development of egg of, 131. 

 Functionality, 343 ; 



in physical systems, 307. 



Galvanotropism, 145. 

 Gases, compression of, 362 ; 



kinetic theory of, 117, 361. 

 Gastrea-theory, 177; 



illustrated, 255 ; limitations of, 256. 

 Genera, stability of, 186. 

 Geometry, Cartesian, 25 ; 



Euclidean, 19, 25 ; perceptual and conceptual limits, 21. 

 Geotropism, 144. 

 Germ-cells, 175 ; 



and soma, 179. 

 Germinal selection, 241. 

 Germ-layers, 177 ; 



theory of, 256. 

 Germ-plasm, a mixture, 240 ; 



stability of, 240. 

 Givenness, 47. 

 Gonads, 179 



