390 THE PHILOSOPHY OF BIOLOGY 



Symbiosis, jj. 



Symbiotic organisms, 88. 



Synapses, in central nervous system, 158, 272. 



Synthetic chemistry, 236, 317. 



System, isolated, 63. 



Systems in development 



equipotential, 139; harmonious equipotential, 139; complex equi- 



potential, 140. 



Taxis, 144 ; 



no perception in, 155 

 Telegraphy, wireless, 355. 

 Temperature of sun, 56 ; 



of space, 57. 

 Thermodynamics, 51 ; 



1st law of, 51 ; 2nd law of, 54, 63, 309, 316; and Maxwell's demons, 



118 ; laws of subject to limitations, 115. 

 Thermodynamical mechanism, the organism not a, 69. 

 Thomson, W., dissipation of energy, 113. 

 Time a series of standard events, 28 ; 



astronomical, 34 ; time differentials, 34. 

 Tissues, evolution of, 223. 

 Tools, nature of, 285 ; 



use of must be learned, 285 ; bodily, 285. 

 Toxins, 36. 

 Transformism, 213. 

 Trematodes, larval stages of, 165. 

 Trial and error, 293 ; 



in reasoning, 293 ; a hypothesis of animal movements, 150. 

 Trigger reactions, 87. 

 Trilobites, an ancient group, 261. 

 Tropisms, 144 ; 



in plants, 269, 279; in moths, 280; and natural selection, 147; and 



movements of caterpillars, 146; an inadequate basis for a theory of 



animal movements, 147. 

 Tunicates, suppressed notochord of, 250. 



Unavailable energy and entropy, 375 ; 



tendency to increase of, 375. 

 Unicellular organisms, energy-transformations in, 177. 

 Unit-characters, 230. 



Van't Hoff's law, 218. 



Variability, 172, 186 ; 



continuous, 188; discontinuous, 188; examples of, 1S7 ; and the en- 

 vironment, 189; independent of the environment, 239; and growth, 

 188 ; tendencies of, 235. 





