io8 THEORETICAL BIOLOGY 



I shall call leading properties those which are necessary 

 and " essential " ; those others which depend only on the 

 character of the substance, I shall call accompanying pro- 

 perties. 



In every language, there occur words which have two 

 meanings, according to the context in which they are found. 

 Isolated, these words have no fixed meaning. In the same 

 way, there are things which are susceptible of two different 

 uses, and these, accordingly, when considered alone, have no 

 fixed function. Taken by themselves, they are not im- 

 plements, but merely objects. 



So long as I hold in my hand a circular, concave piece 

 of glass, it is merely an object. If I set it in a window- 

 frame, it becomes a window-pane ; if I put it on the table, it 

 becomes a saucer, which I can fill with water. In both cases, 

 the object has become an implement. 



It must be borne in mind that the leading and accompany- 

 ing properties change with the change of function. In the 

 case of the window-pane, the transparency is the leading 

 property, and the concavity the accompanying. In the case 

 of the saucer, the reverse is true — the concavity is the chief 

 property and transparency is the accompanying. Function 

 acts like a magnet, which attracts towards it now some 

 qualities and now others. 



Now it appears that the accompanying properties are 

 frequently used by subsidiary functions, and so enter with 

 them into a framework of the implement. Thus transparency 

 becomes a subsidiary function of drinking- vessels, the contents 

 of which we wish to test by the eye. In the same way, 

 concavity becomes the subsidiary function of certain window- 

 panes, which by reflections on the convex side ward off the 

 gaze of the inquisitive. 



The transformation of such subsidiary functions into 

 main functions may easily take place under our very eyes ; 



