!S FACTORS IN VARIATION. 



that these first and second laws of heredity are contra- 

 dictor}' the one of the other, and therefore may be 

 dismissed."* 



But with al! due deference to the great authority of 

 Lankester, it is possible to outline developments of 

 environments which would jirovide stimuli in consonance 

 with the requirements of Lamarck's two laws. It is obvious 

 from geological teaching, that environments have been 

 ratable and unstable, periods of fixation alternating with 

 periods of change : an environment continually changing 

 in a definite direction (such as the rise of the Himalayas, 

 or the transforming of a fertile region into a desert), and 

 then maintaining that changed condition, would enable 

 Lamarckian laws to operate, providing one admits — though 

 this contention would be strongly criticised — that cumulative 

 effects of stimuli through many generations would be more 

 potent than the stimuli apportioned to a single life-time. 



Modern l)iologists have, of course, gone far deeper 

 than Lamarck, for they are giving us the ke}' to the 

 mechanism which brings about functional adaptations, 

 which is not apparently to be found in the '" entelechy "" 

 of the organ'sm. 



In his well-known book on Heredity, J. A. Thomson 

 gives a comprehensive summary of the question, f He 

 suggests that neo-Lamarckians may be identifying post hoc 

 with propter hoc, and states a formidable list of 

 '^ Misunderstandings." Although making judicial 



qualifications, he gives strong support to those scientific 

 writers who. in defiance of Huxley's dictum, have adopted 

 a creed — that acquired characteristics cannot be transmitted. 

 From this standpoint all difficulties can l)e explained. 

 If gout be inherited, then gout is not an acquired character, 

 but a germinal variation made manifest by habits which 

 give a stimulus to its expression. 'Whenever a modification 

 is proved to be transmissible, it should l)e regarded as a 

 congenital variation or else as a '' reappearance."" If 

 transmissibility be demonstrated for unicellular organisms, 



*Ray Lankester : The Kingdom of Man, R.P.A. Reprint, 1912, p.. 70. 

 +.1. A. Thomson: ■■Heredity,"' 190S. Chapter VII. 



