322 The Unity of the Organism 



as chromatin enters into his theory the author is faced 

 toward metaphysics, and metaphysics of a distinctly mysti- 

 cal cast. One of the moderate expressions showing this trend 

 occurs on the first page of the preface: "Some of these 

 miracles [of adaptation] are recited in the second part of 

 this volume to show that the geran evolution is the most 

 incomprehensible phenomenon which has yet been discovered 

 in the universe." The author's emotional attitude toward 

 his theory is to me one of the most significant things about 

 the book. And my criticisms of the theory, implied rather 

 than expressed, are not at all against the fact that an emo- 

 tional attitude is displayed by the author but only that the 

 focal point of this attitude should be chromatin, whether 

 heredity-chromatin or any other — especially when the au- 

 thor is a palaeontologist ! 



Meaning and Criterion of ^^ Mechanism of Heredity" 



If we decide to apply the term "mechanism" to the means 

 by which organisms produce other organisms like themselves, 

 we obviously ought to consider carefully what a mechanism 

 would be that could serve such a purpose. Obviously, I say, 

 such a consideration is due because nowhere else in the world, 

 either the natural or the artificial world, do we find need for 

 any such mechanism. Heredity is surely one of the most 

 distinctive phenomena presented by living beings, so its 

 mechanism must be unique. We have already called atten- 

 tion to the familiar but often ignored fact that "heredity" 

 is the term applied to the universal truth that as the or- 

 ganism unfolds itself from the relatively minute and simple 

 stage known as the germ into the relatively large and com- 

 plex stage known as the adult, it does this in accordance 

 with a scheme or pattern characteristic of the species to 

 which the organism belongs, so that any particular individual 

 in the series resembles those which have gone before it. 

 And this unfolding, we have pointed out, consists essentially 



