152 BIOLOGICAL LECTURES. 



Development is a change and must, therefore, always depend 

 on several components, and hence on combinatiojis of causes or 

 energies. More accurately speaking, we understand by devel- 

 opment the proditctiojt of tmiltiformity . The latter results 

 from every operation, from every combination of energies, at 

 least during and for a short time after the duration of the 

 operation ; and its origin depends on the unequal distribution 

 of energy during its transmission, e.g., in pressure on a body, 

 in heating or electrifying an object, in the radiation of light- 

 rays, etc. It is, therefore, unnecessary in principle to postulate 

 specific energies of developmejit ; this, however, does not pre- 

 clude a possible participation at the same time of special 

 components, as, e.g., the energies of growth, in producing 

 formative diversity during particular phases of organic de- 

 velopment. 



Organic development consists in the production of percepti- 

 ble, typically coitstituted diversity. If we look aside in this 

 place from the conditions of perception (i), typical cojfibinations 

 of causes or energies are indispensable to the origin of " typical 

 diversity." For the specifically constituted nature of this diver- 

 sity, 's^Q.QA^Q, form-producing combinations of cajises are required, 

 and these represent the just-mentioned "formative compo- 

 nents." Now if these formative components be forthcoming 

 in a perfectly typical manner, in kind, magnitude, and arrange- 

 ment, it is self-evident that in the absence of disturbance from 

 without, the constructive diversity produced by these compo- 

 nents must be perfectly typical. 



Accordingly, in any given case, we must trace back each indi- 

 vidual formative process to the special combination of energies 

 by which it is conditioned, or, in other words, to its modi ope- 

 randi ; and each of these modi operandi must be ascertained 

 with respect to place, time, direction, magnitude, and quality. 

 Or, inversely, we may endeavor to determine in the individital 

 structure the special part which is petformed by every modus 

 operandi knoivn to participate in the development of the 

 organism. 



These vtodi operandi, to which we reduce organic formative 

 processes, and hence also the energies which condition them, 



