198 SCIENCE AND PHILOSOPHY OF THE ORGANISM 



case. 1 There indeed occurs a sort of complementary photo- 

 graphy in these algae ; but, though adaptive, it could hardly 

 be said to exceed the limits of " primary phenomena." 



Metabolic regulations. And now we enter the field of 

 regulations in metabolism itself. There are two kinds of 

 outside factors of fundamental importance for all metabolic 

 processes : food is one, and oxygen is the other. And 

 metabolism as a whole is of two different aspects also : it 

 both serves for assimilation proper that is, building up and 

 it supplies the energy for driving the functional machine. 

 It is clear that food alone together of course with the 

 assimilating means of the organism, can account for the 



o o 



first type of metabolism, while both food and oxygen, or 

 some sort of substitute for the latter, as in certain 

 bacteria, supply functional energy. Of course we are not 

 entitled to say that the importance of so-called oxidation 

 or respiration is exhausted by its energetic role : it certainly 

 is not, for if it were, the organism would only be stopped 

 in its functions if deprived of oxygen but would not die. 

 It seems that certain substances always arise in the 

 metabolism, in the processes of decomposition, which have 

 to be burnt up in order not to become poisonous. But 

 we shall return to the phenomena of organic oxidation in 

 another chapter of the book, and shall deal with them from 

 a more general point of view.' 2 



1 The adaptive phenomena discovered by Gaidukow depend upon a real 

 alteration in the formation of pigments. In the (primary) chromatic adapta- 

 tion of pupae of Lepidoptera with respect to the colour of the ground they 

 live upon, we only have the variable effects of pre-established chromatophores 

 (Poulton, Phil. Trans. London, 178 B, 1888 ; Merrifield, Trans. Ent. Soc. 

 London, 1898). The same holds for chromatic adaptations in crabs (Gamble 

 and Keeble, Quart. Journ. Micr. Sci. 43, 1900 ; Minkiewicz, Arch. Zool. exp. 

 et gin. ser. 4, 7, notes, 1907). 



' 2 The theory of oxidation we have shortly sketched here was developed 



