240 SECTION F. 



gan. These authorities justly claim that the power of the inclividnal to 

 play a certain part in the struggle for life may constantly give a definite 

 trend and direction to evolution, and that although the results of a purely 

 individual response to external forces are not hereditary, yet indirectly 

 they may result, in the permanent addition of corresponding powers to 

 the species; — inasmuch as they may render possible the operation of 

 natural selection in perpetuating and increasing those inherent hereditary 

 variations which go further in the same direction than the powers which 

 are confined to the individual. 



Professor Osborn's metaphor in opening this discussion puts the matter 

 quite clearly and will be at once accepted by all Darwinians. If the hu- 

 man species were led by fear of enemies or want of food to adopt an 

 arboreal lile. all the powers of purely individual adaptation would be at 

 once employed in this direction and would produce considerable individ- 

 ual effects. In fact the adoption of such a mode of life would at first 

 depend on the existence of such powers. In this way natural selection 

 would be compelled to act along a certain path, and would be given time 

 in which to produce hereditary changes in the direction of fitness for 

 arboreal life. These changes would probably at first be chiefiy functional, 

 as Mr. Cunningham has argued (in the Preface to his Translation of 

 Eimer). On these principles we can understand the arboreal kangaroo 

 (Dendrolagus) found in certain islands of the Malay Archipelago, which 

 is apparently but slightly altered from the terrestrial forms found in Aus- 

 tralia. Professor Osboru has alluded to the arboreal habits said to have 

 been recently acquired by Australian rabbits ; these and the similar modi- 

 fication in liabits of West Indian rats, are further examples of individual 

 adaptive modification which may well become the starting point (in the 

 sense applied above) of specific variation led by natural selection in the 

 definite direction of more and more complete adjustment to the necessi- 

 ties of arboreal life. Although this conclusion seems to me to be clear 

 and sound, and the principles involved a substantial gain in the attempt 

 to understand the motive forces by which the great process of organic 

 evolution has been l)rought about, I cannot adnxit that the importance 

 of natural selection is in any way diminished. I do not believe that these 

 important principles form any real compromise between the Lamarckiau 

 and Darwinian positions, in the sense of an equal surrender on either side, 

 and the adoption of an intermediate position. The surrender of the 

 Laraarckian position seems to me complete, while the considerations now 

 advanced only confer added siguiticance and strength to the Darwinian 

 standpoint. 



I propose to devote the remainder of the time at my disposal in support 

 of the conclusion that the poAver of individual adaptation possessed by 

 the organism forms one of the highest achievements of natural selection 

 and cannot in any true sense be considered as its substitute. Professor 

 Baldwin and Prof. Lloyd Morgan thoroughly agree with this conclusion 



