156 SECTIONAL ADDRESSES. 



in general — may be defined as a single mutational step which owes its 

 origin not to discovery, but to a combining of structures or devices already 

 in existence. The result is objectively a structural combination, which is 

 preceded subjectively by the action of the mind in recognising the advan- 

 tages and the possibilities of the hybridisation, and in thinking out the 

 method of efiecting it. 



We may now inquire whether we are any nearer to the establishment 

 of criteria of independent evolution in respect of artefacts — whether 

 coincidence through mutation is more or less likely to occur than 

 coincidence through variation in form. Except in so far as variation is 

 limited by the form and nature of materials employed, and by the 

 functional eflaciency of the completed artefact, it has a very wide range, 

 and it may give rise to features that are functionally meaningless, or even 

 detrimental. Mutations, on the other hand, are much more closely deter- 

 mined by functional considerations ; they result, as we have just noted, 

 either from chance discovery that a modification of a particular kind is 

 advantageous (free-mutations) or from a prediction that a modification 

 by transfer and combination may be of value (cross- mutations). Useless 

 mutations are much less likely to survive, even if hit upon, than are 

 useless variations. 



It is one of the provinces of variation to add to the efiectiveness of 

 characters which have appeared as a result of mutation, but it may also 

 develop characters in such a direction as to lead towards, or away from, 

 another mutation. The variational development of the push-quern into 

 the saddle-quern was clearly away from any line of evolution that could 

 lead to the mutational step, or steps, that produced the rotary quern. 

 Variations and mutations react upon each other, but the process is not 

 one which leads to parallelism or convergence. 



As regards mutational criteria, it is evident that the occurrence of 

 free-mutations depends upon the state of development of the artefact in 

 which they appear. They may be primarily due to some feature of 

 construction or material which gives rise to a chance suggestion for 

 improvement, or this may arise through substitution, and their adoption 

 may depend upon a variety of social as well as material conditions. In 

 the case of cross-mutations there can only be a combination of features 

 or devices if these are present in the same region at the same time ; and 

 where the case is one of simple adaptational transfer, there must be present 

 in the appliance that profits by the mutation some feature of structure 

 or working which suggests the possibility. 



In a further treatment of the subject of inventions it would have been 

 desirable to discuss such factors as change of function, change in method 

 of use, and numerical mutation, but sufficient has been said to indicate the 

 analytical method of approach. 



If we take into account all the factors involved in the development 

 of artefacts, even in simple cases, independent evolution involves 

 coincidences, few or many. It is also clear that the further the artefact 

 from the primary mutation which began it, that is to say, the longer the 

 series of variational and mutational changes that has been undergone, 

 the bigger the draft on coincidence. Nevertheless we are still unable to 

 point to definite mutational criteria, and to say that it is impossible that 

 some particular mutation — and especially a primary mutation — should 



