INHERITANCE 221 



whole," though this ideal whole will never be realised in 

 its proper wholeness. 1 



But there is no need to recur to the " ideal whole " in 

 many other cases of adventitious restitution in plants. 

 On isolated leaves of the well-known begonia, a whole plant, 

 containing all the essential parts, may arise from any single 

 cell 2 of the epidermis, at least along the veins, and in some 

 liverworts it has been shown by Vochting, that almost 

 every cell of the whole is able to reproduce the plant, as 

 is also the case in many algae. 



In the animal kingdom it is chiefly and almost solely 

 the phenomena of regeneration proper which offer typical 

 instances of our systems, since adventitious restitution, 

 though occurring for instance in the restitution of the lens 

 of vertebrates from the iris, and though connected also with 

 the events in regeneration proper, 3 is of but secondary 

 importance in animal restitution, at least, if compared with 

 restitution in plants. If we study the regeneration of a 

 leg in the common newt, we find that it may take place 

 from every section, the point of amputation being quite at 



1 The "ideal whole" is also proved to exist, if any given " Anlage," say 

 of a branch, is forced to give origin to a root, as has really been observed in 

 certain plants. This case, like many other less extreme cases of what might 

 be called "compensatory heterotypy," are best to be understood by the aid 

 of the concept of "prospective potency." It is very misleading to speak of 

 a metamorphosis here. I fully agree with Krasan about this question. See 

 also page 112, note 1, and my Organ. Regul. pp. 77, 78. 



2 Winkler has discovered the important fact, that the adventitious buds 

 formed upon leaves may originate either from one single cell of the epidermis 

 or from several cells together ; a result that is very important with respect 

 to the problem of the distribution of "potencies." 



3 The "regeneration" of the brain of annelids for instance is far better 

 regarded as an adventitious formation than as regeneration proper : nothing 

 indeed goes on here at the locality of the wound ; a new brain is formed out 

 of the ectoderm at a certain distance from it. 



