GROWTH IN TIME OF THE TOTAL ORGANISM 



215 



any explanation in physico-chemical terms. Essentially, however, restitutive regeneration 

 is of the same nature as physiological regeneration by which the organism is maintained 

 in a steady state in a continuous breaking-down and replacement of components. Physio- 

 logical and restitutive regeneration are governed by the same principles, the difference only 

 being that component parts are "worn out" and replaced as part of the normal life process 

 in the first case, and accidentally or experimentally removed in the second. A good example 

 of equifinality in regeneration is presented by experiments on earthworms : the number 

 of regenerated segments is independent of the number originally present so that regenera- 

 tion comes to a stop when a number of 90 segments is reestablished, irrespective of whether 

 50, 40, 30, etc., segments were amputated (Moment, 1946). 



Lowest stratum 



Fig. 21. Evolutionary equifinality. Convergence (evolution of three-lobed species) in 



independent series of ammonites. Left: Paradymenia abeli, Wocklumeria sphaeroides, Epiwock- 



lumeria applaiiata. Right: Kamptoclymenia endogena, K. trivaricata, Parawocklumeria paradoxa. 



After Schindewolf from Rensch, 1954. 



It appears that similar rules even apply to evolution. It has been emphasized by Schinde- 

 wolf that similar final stages may be reached in independent evolutionary series, as found 

 e.g. in corals and the irregular types of ammonites (Fig. 21). Since a particular adaptive 

 value can hardly be attributed to the formations eventually reached in these evolutionary 

 series, it may be surmised that evolutionary equifinality represents a tendency toward 

 establishment of singular states of genie balance which may be reached if different ways. 



Many of such phenomena are, of course, not amenable to quantitative treat- 

 ment. Possibly, however, they can be envisaged as difTerent expressions of the same 

 basic principles. 



Literature p. 253 



