THE PRESIDENTIAL ADDRESS. 13 



If the simile I have used would sound strange in Darwin's ear, could he 

 hear it, the underlying meaning would be familiar to him. Over and 



over again he declared that he did not know how ' variations ' 



Machine and i i r i_i 0.1, 1 1 i t. 



Animal were produced, favourable or otherwise ; nor could he have 



Evolution known, for in his time hormones were undreamt of and 

 contrasted. 



experimental embryology scarcely born. With these recent 



discoveries new vistas opened up for students of Evolution. The moment 

 we begin to work out the simile I have used and compare the evolutionary 

 machinery in a motor factory with that which regulates the development 

 of an embryo within the womb, we realise how different the two processes 

 are. Let us imagine for a moment what changes would be necessary 

 were we to introduce ' embryological processes ' into a car factory. 

 We have to conceive a workshop teeming with clustering swarms of 

 microscopic artisans, mere specks of living matter. In one end of this 

 factory we find swarms busy with cylinders, and as we pass along we note 

 that every part of a car is in process of manufacture, each part being 

 the business of a particular brigade of microscopic workmen. There is 

 no apprenticeship in this factory, every employee is born, just as a hive- 

 bee is, with his skill already fully developed. No plans or patterns are 

 supplied ; every workman has the needed design in his head from birth. 

 There is neither manager, overseer, nor foreman to direct and co-ordinate 

 the activities of the vast artisan armies. And yet if parts are to fit when 

 assembled, if pinions are to mesh and engines run smoothly, there must 

 be some method of co-ordination. It has to be a method plastic enough 

 to permit difficulties to be overcome when such are encountered and to 

 permit the introduction of advantageous modifications when these are 

 needed. A modern works manager would be hard put to were he asked 

 to devise an automatic system of control for such a factory, yet it is just 

 such a system that we are now obtaining glimpses of in the living work- 

 shops of Nature. 



I have employed a crude simile to give the lay mind an inkling of 

 what happens in that ' factory ' where the most complicated of machines 

 Th are forged — the human body and brain. The fertilised 



Machinery of ovum divides and redivides ; one brood of microscopic 

 " living units succeeds another, and as each is produced the 

 units group themselves to form the ' parts ' of an embryo. Each ' part ' 

 is a living society ; the embryo is a huge congeries of interdependent 

 societies. How are their respective needs regulated, their freedoms 



