I50 BIOLOGICAL LECTURES. 



In accordance with Spinoza's and Kant's definition of mech- 

 anism, every phenomenon underlying causality is designated 

 as a mechanical pJietio^nenon ; hence the science of the same 

 may be called mechanics. Since only phenomena underlying 

 causality are capable of investigation, and hence alone may be 

 made the subject of an exact science, and since the production 

 of fonn constitutes the essential feature of development, it is 

 quite permissible to call the science of the causes of form 

 developmental mechanics. 



Since, moreover, physics and chemistry reduce all phenom- 

 ena, even those which appear to be most diverse, e.g., mag- 

 netic, electrical, optical, and chemical phenomena, to move- 

 ments of parts, or attempt such a reduction, the older more 

 restricted concept of mechanics in the physicist's sense as 

 the causal doctrine of the movements of masses, has been 

 extended to coincide with the philosophical concept of mechan- 

 ism, comprising as it does all causally conditioned phenomena, 

 so that the words "developmental mechanics" agree with the 

 more recent concepts of physics and chemistry, and may be 

 taken to designate the doctrine of all formative phenomena. 



Inasmuch as we call the causes of every phenomenon forces 

 or energies, we may designate as the general problem of devel- 

 opmental mechanics the ascertaijiment of the formative forces or 

 energies. In so far, however, as forces or energies are only 

 known to us by their effects, i.e., every kind of force by its 

 specific mode of operating, the problem may be defined as the 

 ascertainment of the formative modi operandi. 



In accordance with this statement, a general, not quantita- 

 tive, but in the first instance, merely qualitative causal explajia- 

 tion will always consist in tracing back a particular phenome- 

 non to modi operandi of more general validity, i.e., to such as 

 operate constantly, also in many other processes, and hence 

 under the same conditions, at all times and in all places, and in 

 the same manner. Such modes of operating may be called 

 " constants of operation " (" Wirkungsbestandigkeiten "). 



TJiese constant modi operandi tvhicJi follow from the proper- 

 ties of the components and hence of necessity, — these so-called 

 uniformities of nature, — are usually called ''natural laws'' 



