no THEORETICAL BIOLOGY 



THE LIVING ORGANISM 



The framework of our human implements is intelligible 

 chiefly because they all refer to some very familiar human 

 function. The actions of implements are never their own 

 actions, but are merely counter-actions to our human doings, 

 which in some way or other they support, refine or expand. 

 And so we are never in any doubt about there being a main 

 function ; we recognise quite clearly the part-functions and 

 subsidiary functions, because throughout we recognise human 

 action as the measure and basis constituting the cause of all 

 the counter-actions, down to the smallest detail. The way in 

 which the counter-actions express themselves in the frame- 

 work is determined by the properties of the material from 

 which we construct the implement. 



Morphology. This certainty that a principal function 

 forms the scaffolding around which the other functions group 

 themselves, is lacking when we deal with living beings, and 

 we very soon feel the effects. As a matter of fact, a new 

 science, " morphology," has developed from the mere de- 

 scription of the framework of organisms, a science which, in 

 contrast to the theory of function, is not applicable to our 

 human implements. 



The fundamental principles on which the classification of 

 living things was undertaken sprang from this science. When 

 we divide up animals into five-rayed, four-rayed and two- 

 rayed (bilaterally symmetrical) and segmented animals, we 

 are deaUng with things from a point of view that has nothing 

 to do with the functions of the animals. 



At a very early date the conviction forced itself on 

 zoologists that a classification of animals must be carried out 

 not according to functional, but according to morphological 

 features ; not the " analogy " of the anatomical parts, but 

 their " homology," is to be the standard for classification. 



