42 THE FOUNDATIONS OF ZOOLOGY 



* vitality ' (yjrvx^e) has reached the end of its long career of useful- 

 ness. 



" I admitted long ago that it is as truly a property of a bird to 

 build a nest as it is a property of water to freeze ; but our interest 

 in the nest lies in its fitness for maintaining the species. I hear 

 it said among you that science has nothing to do with the Why, 

 but only with the How ; but we can surely give answers to the 

 questions 'Why do men make and buy watches?' — 'Why do 

 birds pursue their prey ? ' — ' Why do they flee their enemies ? ' 



— and 'Why do they make nests?' — answers which are good and 

 sensible, although they are incomplete. 



"The naturalists of your day are adding continually to the 

 overwhelming evidence for a truth which was unsuspected in mine 



— the mutability of species and the continuity of life. If I could 

 now publish a new edition of the ' Parts of Animals,' I should 

 treat with more consideration than they seemed to merit two 

 thousand years ago the views of my contemporaries who held that 

 extermination and survival have a good deal to do with fitness, 

 but I should still contend that the study of fitness is the true 

 aim of biology." 



This comment on the current interpretation of the essay on 

 "The Physical Basis of Life" seems to me to be good common 

 sense and therefore good science ; and it also seems to me to be 

 a legitimate application of the teachings of the " Parts of Animals." 



Huxley makes many references to the problems of biology in 

 later essays, but space will permit us to examine none except the 

 last. In 1894 I find certain Prolegomena (IX. i, 1894) in which it 

 is easy to read between the lines clear indications that, notwith- 

 standing the period represented by the essay on "The Physical 

 Basis of Life," Huxley ended as he began, — almost, if not alto- 

 gether, in the old-fashioned conviction that living things do, in 

 some way and in some degree, control or condition inorganic nature ; 

 that they hold their own by setting the mechanical properties of 

 matter in opposition to each other, and that this is their most 

 notable and distinctive characteristic. He says the flora of the 

 region where he writes was in a " state of nature " until three or 

 four years before, when the " state of nature was brought to an 

 end, so far as a small patch of soil is concerned, by the interven- 



