REPAIR IN EVOLUTION 67 



breakdown is one of the basal laws of all construction 

 and organization. Yet none can read engineering without 

 observing that all development has followed such lines. 

 As new stresses are introduced, failure is threatened, and 

 steps are taken to obviate disaster. What is a patch on one 

 engine becomes organic in the next. Since waste of energy 

 can be looked on as pathological, we observe the reaction 

 in the engineer against such failures, as the atmospheric 

 engine is succeeded by improved forms ending in the quad- 

 ruple expansion engine. Many other instances could be 

 adduced in general or special engineering evolution; but 

 the best illustration of the facts which need elucidation 

 can perhaps be found in Gothic architecture. If such a 

 demonstration of this general principle can be made it 

 will go far to obviate the objection, very likely to be urged, 

 that what occurs in human construction has no relevance 

 to the living organism, especially if it can be suggested 

 forcibly that human intelligence is in itself a reaction, 

 and that the law obtains in developments of all kinds. 

 It is, indeed, not going too far to declare that there is no 

 real qualitative difference between the cytoplasm of a test- 

 bearing protozoon as it elaborates its peculiar envelope 

 and the general cerebral protoplasm of a human com- 

 munity constructing some great edifice. That trial and 

 error are at the base of evolution is indeed implied in 

 the current teaching as to variation, and its extension to 

 intellectual processes will surprise no worker who has had 

 to deal experimentally with the unknown. We may expect, 

 but never know, where to look for failure till we see it. 

 When it is seen we can do our best, as reacting agents, to 

 remedy it. Having said so much, and leaving aside 

 the wider implications of such views, we may turn to such 

 a problem of construction as the evolution of a cathedral, 



