120 SCIENCE AND PHILOSOPHY OF THE ORGANISM 



and the same prospective potency distributed equally over 

 their elements. If we now borrow a very convenient term 

 from mechanics, and call any part of the organism which 

 is considered as a unit from any morphogenetic point of 

 view, a morphogenetic " system" we may sum up what 

 we have learnt by saying that both the blastoderm of the 

 echinoderms, at least around its polar axis, and also the 

 germ-layers of these animals, are " systems ' possessing an 

 equal potentiality in all of their elements, or, in short, that 

 they are equipotential systems. 



But such a term would not altogether indicate the real 

 character of these systems. 



Later on we shall analyse more carefully than before 

 the distribution of potencies which are the foundation both 

 of regeneration proper and of adventitious growth, and 

 then we shall see that, in higher plants for instance, there 

 is a certain " system ' : which may be called the organ 

 proper of restitutions, and which also in each of its elements 

 possesses the same restoring potency ; I refer to the well- 

 known cambium. This cambium, therefore, also deserves 

 the name of an " equipotential system." But we know 

 already that its potencies are of the complex type, that they 

 consist in the faculty of producing the whole of such a 

 complicated organisation as a branch or a root, that the 

 term " equipotential system ' is here only to signify that 

 such a complicated unit may arise out of each of the cells 

 of the cambium. 



The potencies we have been studying in the blastula or 

 gastrula of echinoderms are not of the complex type : our 

 systems are equipotential to the extent that each of their 

 elements may play every single part in the totality of what 



