DOMAIN OF EVOLUTIONARY HYPOTHESIS 111 



particularly by Haberlandt, into the ' sense organs of 

 plants/ we will go more closely into the matter. 



What, in the opinion of modern biologists 

 and particularly also of Haberlandt is ' excitability ' 

 (ReizbarJceit) and what does its presence imply for the 

 organism which possesses it ? 



What signifies the construction of particular ' organs ' 

 for the reception of special stimuli, such as that of light, 

 mechanical pressure, breakage, gravity, etc., for the 

 possession of actual sense faculties recognition and 

 voluntary power of effort ? 



From what has already been said regarding the 

 relation of the organisms to inorganic matter and 

 the general forces of nature, such as light, warmth, 

 gravity, there is a double deduction. 



Firstly, the organism needs, if it will be active, 

 an influx of energy from outside ; secondly, it uses 

 this energy for its own purposes, such as building 

 material for instance, the formation of digestive 

 (assimilating) tissues, of conducting systems for the 

 nutritive matter through the whole body, of germ 

 cells from which new individuals of its kind result, etc. 



Oxygen, hydrogen, carbonic acid, sulphur, phos- 

 phorus, lime, and the other elements which exist in 

 the organism, also light, energy, electricity, gravity, 

 have quite obviously in themselves no tendency to 

 build tubes for water conduction or blood circulation, 

 or a leaf which breathes and assimilates, or an egg and 

 seed-cell of a fir tree. If, despite this, the chemical 

 material is necessary so that the activity of the organism 



