EXPERIMENTAL MORPHOGENESIS 101 



so. By such reasoning, indeed, the temperature, or sodium, 

 might be called the " cause " of any special process of 

 morphogenesis. It, therefore, seems to be of little use to 

 give the name of cause to that factor of any necessary 

 constellation of events which accidentally happens to be 

 the last that is realised. But what is to be done then ? 



Might we not say that the cause of any morphogenetic 

 process is that typical property, or quality, or change, on 

 which its specific character depends, on which depends for 

 example, the fact that now it is the intestine which appears, 

 while at another time it is the lens of the eye ? We might 

 very well, but we already have our term for this sort of 

 cause, which is nothing else than our prospective potency 

 applied to that elementary organ from which the new 

 process takes its origin. The prospective potency indeed 

 is the truly immanent cause of every specification affecting 

 single organogenetic processes. But we want something 

 more than this. 



We may find what we want by considering that each 

 single elementary process or development not only has its 

 specification, but also has its specific and typical place in 

 the whole its locality. Therefore we shall call the " cause ' 

 of a single morphogenetic process, that occurrence on which 

 depends its localisation, whether its specific character also 

 partly depends on this " cause " or not. 1 



This definition of " cause }: in morphology may be 

 artificial ; in any case it is clear. And at the same time 

 the concepts of the prospective potency and of the " means ' 

 of organogenesis now acquire a clear and definite meaning : 



In certain cases part of the specific feature of the process in question may 

 also depend on the " cause " which is localising it, e.g. in the galls of plants. 



