Modification and Variation. 321 



the variable in that direction. Lamarckian palaeontologists 

 are apt to overlook this fact that natural selection produces 

 determinate variation. 



19. The transmissionist fixing his attention first on the 

 modification, and secondly on the fact that organic effects 

 similar to those produced by the modification gradually 

 become congenitally stereotyped, assumes that the modifi- 

 cation as such is inherited. 



20. It is here suggested that the modification as such 

 is not inherited, but is the condition under which congenital 

 variations are favoured and given time to get a hold on 

 the organism, and are thus enabled by degrees to reach the 

 fully adaptive level. 



When we remember that plastic modification and 

 germinal variation have been working together all along 

 the line of organic evolution to reach the common goal of 

 adaptation, it is difficult to believe that they have all 

 along been wholly independent of each other. If the direct 

 dependence advocated by the transmissionist be rejected, 

 perhaps the indirect dependence here suggested may be 

 found worth considering. 



It only remains to say a few words concerning the 

 bearing of the above discussion on our special subject, 

 habit and instinct. Habits are of the nature of individual 

 modifications rendered possible by intelligent adaptation 

 to the conditions of life ; instincts are due to congenital 

 variations of germinal origin. But instinctive activities 

 so often take the line which is marked out by adaptive 

 habit, that it is not surprising to find many who believe 

 that instinct is neither more nor less than inherited habit. 

 Special modes of flight, special ways of bathing, peculiar 

 methods of courtship, specific types of behaviour; these 

 and many other activities may well be regarded as having 



