16 ESSAYS OF A BIOLOGIST 



a personal creator (in which case, be it noted, 

 the idea or the plan often appears to our intellect as 

 unreasonable and indeed stupid); or finally that it 

 implies community of origin with later divergence 

 of development. When we are dealing with the 

 smaller sub-divisions of some larger group, this 

 method too gives us information of the same order 

 of accuracy as does paleontology: but when we try to 

 understand the relationships of these larger groups, 

 then we are forced to renounce any claim to detailed 

 knowledge. In broad outline, however, a great deal 

 still remains, and this broad outline we can employ 

 for our valuation of the whole sweep of biological 

 progress, just as we can use the greater accuracy of 

 vertebrate paleontology and comparative morphol- 

 ogy to fill in the detail within a restricted field of 

 its operation. From these various evidences, direct 

 and indirect, we can paint for ourselves a picture of 

 the evolution of life which, in spite of inevitable 

 gaps and errors, is in its main features adequate and 

 true. 



Let us not be misled by the fact that disputes can 

 and justifiably do arise over details: as Professor 

 Bateson put it recently^: — 



"If the broad lines do not hold, then we must sink 

 into irrationality or turn to flagrant supernatural- 



ism.'' 



Let us then remind ourselves of some of these 

 broad lines. 



* Bateson, '22. 



