FORM REGULATION IN CER1ANTHUS. 73 



occur in the membrane after its formation bring into play other 

 factors. These need not be considered here, however. Certainly 

 the phenomena are far from being adaptive or teleological in any 

 sense although the closure of the cut might appear at first glance 

 to be an adaptation. It is difficult at present to see how they 

 can be due to anything except simple physical conditions, though 

 it is possible that increased knowledge may afford another explan- 

 ation. Provisionally then we may regard the delicate thin mem- 

 brane which appears in the angles between cut surfaces as pos- 

 sessing some of the properties of a fluid and as subject, at least in 

 large degree, to the laws of capillarity. 



Whether these suggestions are correct or not, the two facts 

 above mentioned are of great importance, viz., that regeneration 

 of new tissue from cut surfaces occurs only when two surfaces 

 are in contact, and that the new tissue cannot extend indefinitely 

 between diverging cut surfaces but ceases at a certain point de- 

 termined by the angle of divergence of the two surfaces and the 

 (physical) quality of the membrane, /. e., is different in different spe- 

 cies. The only possible inference from these facts is that all con- 

 ditions for regeneration are not given in the living tissues them- 

 selves, nor in these plus the normal environment as a whole, but 

 that the formation of new tissue from a cut 'surface is probably 

 dependent upon certain simple physical conditions similar to 

 those which govern the existence of a liquid film between two 

 diverging boundaries. 



Healing of the cut surface does not require these conditions ; 

 for this the necessary conditions, which are very probably also 

 primarily due to capillarity, are established by the cut itself. The 

 same conditions are not, however, adequate for the formation of 

 a membrane of new tissue from the cut surface. 



In this case then the conditions for new growth and closure 

 of a wound are to be found, not in the absence of a certain part, 

 nor in the presence of a special stimulus at the cut surface, but 

 in simple, external, physical relations of parts. Discussion of the 

 bearing of these facts may be postponed to another time. Atten- 

 tion may be called, however, to the difficulty of reconciling these 

 facts with the neo-vitalistic theories of life and especially with that 

 of Driesch which is based upon the phenomena of form-regula- 



