xlvi MUTATION, MENDELISM, ETC. 



maintain that the obviousness of these advantages 

 satisfactorily explains why the cork layer is produced.' 

 On the contrary, these advantages, if scientifically proved 

 to be conferred, probably do explain why it is that the 

 power of forming cork was selected, and has come to 

 be a character of the higher plants. They do not 

 explain how the layer is formed ; but, so far from barring 

 the way, it is quite clear that the proof of important 

 advantages conferred adds immensely to the interest 

 of the cork, and greatly increases the probability of the 

 student undertaking an investigation into the sequence 

 of events by which it is produced in the individual plant. 1 

 The attempts to answer the questions 'Why' and 

 ' How ' ' To what end ? ' and ' In what way ? ' by no 

 means interfere with each other. These two sides of 

 investigation, on the contrary, provide mutual assistance 

 and encouragement. There are always these two 

 questions to be answered with reference to any natural 

 phenomenon, and both must be answered if the facts are 

 to be fully understood. Any one who is foolish enough 

 to maintain that the answer to one of these questions 



1 My friend Professor S. H. Vines, F.R.S., has kindly drawn my attention 

 to the following interesting and relevant passages from Whewell's History 

 of the Inductive Sciences (vol. iii, 3rd edition, p. 390) : c Cuvier's merit 

 consisted, not in seeing that an animal cannot exist without combining 

 all the conditions of its existence ; but in perceiving that this truth may 

 be taken as a guide in our researches concerning animals : that the 

 mode of their existence may be collected from one part of their structure, 

 and then applied to interpret or detect another part.' This bears out the 

 argument that knowledge of the use or purpose of a structure or a pro- 

 perty acts as a stimulus to investigation. 



Furthermore, in his Philosophy of the Inductive Sciences, Whewell 

 says (vol. ii, p. 78), ' The idea of a Final Cause is an essential condition 

 in order to the pursuing our researches respecting organized bodies.' 

 Again (p. 90), ' The doctrine of a purpose in organization has been some- 

 times called the doctrine of the Conditions of Existence! 



