ISO 



THE ORIGIN AND EVOLUTION OF LIFE 



The ever changing velocity and changing bodily form and 

 function in character complexes are to be regarded as expressions 

 of physicochemical energy resulting from the actions, reactions, 

 and interactions of different parts of the organism. As we 

 have repeatedly stated, these changes proceed according to 

 some unknown laws. The only vista which we enjoy at pres- 



sent of a possible fu- 

 ture explanation of the 

 causes of character 

 origin, character veloc- 

 ity, and character co- 

 operation is through 

 chemical catalysis, 

 namely, through the 

 hypothesis that all ac- 

 tions and reactions of 

 form and of motion 

 liberate specific cata- 

 lytic messengers, such 

 as ferments, enzymes, 

 hormones, chalones, 

 and other as yet un- 

 discovered chemical messengers, which produce specific and 

 cooperating interactions in every character complex of the organ- 

 ism and corresponding predispositions in the physicochemical 

 energies of the germ; in other words, that the chemical accelera- 

 tors, balancers, and retarders of body cell development also 

 affect the germ. 



In our survey of the marvellous visible evolution of the 

 vertebrates we may constantly keep in our imagination this 

 conception of the invisible actions, reactions, and interactions 

 of the hard parts of the structural tissues, which are preserved 



Fig. 39. Proportional Adaptation in the 

 Fingers of a Lemur. 

 This peculiar hand of the Aye-Aye {Cheiromys) of 

 Madagascar affords an excellent example of un- 

 equal velocity in the development of adjacent 

 characters. In this hand each finger has its own 

 proportionate rate of evolution. The thumb 

 (upper) is extremely short; the index finger is 

 normal; the middle finger is excessively slender, 

 in adaptation to a very special purpose, namely, 

 for insertion into small spaces and crevices in 

 search of larv£e; the fourth and fifth fingers (two 

 lower) are normal. 



