386 Allgemeines. 



crystals, but pseudo-crystals oi organic substances are known 

 in which that degree of mathematical constancy characteristic 

 of simple inorganic salts does not obtain. 



The form oi the living organism by its very constancy can 

 hardly be of a very different order, though the relationship of 

 matter and force must be enormously more complex than in 

 a crystal. The view that the form characteristic of an organism 

 is an inherited property is no more an explanation of the 

 phenomenon itself then it would be to assert that the crystals 

 of common salt deposited from Solution owe their form to the 

 hereditary transmission of the form of the parent crystals used 

 to make the Solution. The form is transmitted in neither case ; 

 all that is handed on is the material, and when placed under 

 suitable conditions, out of the material arises in the one case 

 the necessary crystalline form, in the other the necessary living 

 form. 



That the living form is immensely more complex is partly, 

 perhaps largely, due to the continual disturbing influences of 

 those chemical changes that accompany the process of ontogeny. 

 But in healthy iife the chemical march of events pursues a 

 fairly even, albeit a complex course; when it does become 

 deranged, we speedily observe indications of this in — an 

 alteration ofform. For example, the abnormal growth of 

 galls is due partly to specific Stimuli on the part of the attacking 

 animal, which directly modify the normal sequence of events in 

 the tissues affected and so lead to growths characteristic 

 mutually of the plant and the animal concerned. An other 

 example is found in Mucor racemosus when immersed in a 

 nutritive medium; and the work of Klebs on algae shows how 

 closely the various forms are bound up with the function of 

 nutrition. One may regard the material basis of an organism 

 as analogous to a mechanism tuned to respond to certain 

 Stimuli in certain ways, the final character of each individual 

 or of each organ being the result of particular Stimuli acting 

 on particular kinds of mechanism. 



In the material substratum of a plant or animal we have 

 to deal with vastly complex bodies diverse in different organisms, 

 capable of constantly undergoing changes as evidenced by 

 growth and decay. These functions of metabolism are universally 

 characteristic of living things and are associated with the proto- 

 plasmic body. And therein some unity of ground plan may be 

 indicated and the clue is probably to be sougth in the chemical 

 mechanism of the protoplasm itself. Although we are at present 

 unable to make any probably accurate guess as to the precise 

 nature of the mechanism nevertheless we can hardly escape the 

 inference that in some sort it has a real existance, when we 

 reflect upon the diverse results produced on different organisms 

 or on different parts of the same organism by relatively simple 

 and identical Stimuli, e. g. gravitation. 



