THE LIVING SUBSTANCE. 141 



[139] The whole series of structures which increase the 

 range of organisms' intercourse with external environment, that 

 is, the sensory organs, have peculiar reference to extension of 

 the control of supplies for internal environment. The extension 

 and intensification of irritable reaction, which are seen in the 

 ectosarcal structures of sense organs, practically annihilate dis- 

 tance and bring knowledge of supplies for which, if they must 

 be in actual physical contact, the creature might wait long and 

 perhaps hopelessly. As when a moth is drawn by odours too 

 delicate for our perception, to its mate many yards away ; or 

 a wild beast scents its prey, or an eagle marks his quarry, 

 from afar. 



[140] According to the kind, and the distribution in envi- 

 ronment, of its supplies, the character of the substance organs 

 or structures of the organism are adjusted. In the plant and 

 animal kingdom in their most familiar forms these things are 

 strikingly marked. In both, the same general laws hold good, — 

 that is the organisms select, not only what may serve for imme- 

 diate use, but what may be laid up for use when the source of 

 supplies is cut off from them, — or so lessened as to threaten 

 the species by too fierce warfare amongst its units for the scant 

 material : In both, the best efforts of the machine are spent 

 for the needs of perpetuation areas: In both, the kind and 

 quantity of the nutriment cause curious differences in the form 

 and character, even the sex, of these areas. 



(a) Yet in each kingdom the characteristic choice is along 

 the direction of those elements, or opportunities, surrounding 

 it, the pursuit of which, as well as their chemical constitution 

 when secured, tend to preserve and develope existing types of 

 organisms. And with the character of substance habit in all 

 these things goes the peculiar character of the ectosarcal 

 structures, and the form of the machine as a substance 

 device. 



(b) The animal kingdom has chosen the secondary, the un- 

 certain, the motile, scattered, opportunities of environment. 

 The plant kingdom, as a whole, has chosen to develope its 

 powers along the lines of constant, stable, and, one may say, 

 almost omnipresent conditions. 



