EXPERIMENTAL MORPHOGENESIS 137 



parts of the skeleton of the hand or foot, but also the 

 special form of each element is typical, e.g. the form of 

 each single bone of the foot ; and, on a purely chemical 

 theory of morphogenesis the sufficient reason for the 

 production of typical form in such a sense would be want- 

 ing. For atoms or molecules by themselves can only 

 account for form which is arranged, so to speak, according 

 to spatial geometry- -as in fact they do in crystallography ; 

 but they can never account for form such as the skeleton 

 of the nose, or hand, or foot. You will answer me perhaps, 

 that there may be non-chemical agents in the germ, 1 re- 

 sponsible for typical form-localisation, but by such reasoning 

 you would be departing from a purely chemical theory. 

 Our next paragraph will be devoted to this side of the 

 question. 



That is the principal reason for rejecting all sorts of 

 chemical morphogenetic theories put forward to explain the 

 problem of localisation; it is more explicit, and therefore, 

 I suppose, still more convincing than the more general con- 

 sideration that the very fact of restitutions in itself must 

 contradict the hypothesis that a disintegration of compounds 

 might be the directive agency in morphogenesis. To sum 

 up : Specificity of organic form does not go hand-in-hand 

 with specificity of chemical composition, and therefore cannot 

 depend on it ; and besides that, specific organic form is 

 such that it can never be explained by atomic or molecular 

 arrangement in the chemical sense ; for, to state it in a 

 short but expressive manner, the " form ' of an atom or 

 molecule can never be that of a lion or a monkey. To 



1 Besides the specified poles determined by the polar-bilateral structure 

 of the protoplasm. 



