No.G33] INHERITANCE IN THE OSTRICH 311 



In general, correlated structural relationships, estab- 

 lished through long ages, will act as a vis inertia to the 

 introduction of acquired changes ; they will represent so 

 much heritable, inherent tendency which has to be over- 

 come before any new relationship of parts can be estab- 

 lished. Life-time changes of habit or of environment, as 

 in the assumption by man of the erect habit, or the taking 

 to water of a former terrestrial organism, are the con- 

 ditions which will be conducive to acquired changes be- 

 coming transmissible, compared with those under which 

 the responses are temporary, or continued for a few gen- 

 erations, or are the result of mutilation. 12 Any tem- 

 porary structural relationship established, as in the de- 

 caudation experiments of Weismann and others, would 

 manifestly be incapable of overcoming those deeper rela- 

 tionships which, with each new generation, find their ex- 

 pression in a complete tail. As Professor T. H. Morgan 13 

 points out, the theory of the inheritance of acquired char- 

 acters 4 'is one that has the great merit of being capable 

 of experimental test," but he allows that "modern La- 

 marckians are justified in claiming that the validity of 

 the theory can only be tested by experiments in which 

 the organism is subjected to influences extending over a 

 considerable period." The hypothesis here submitted is 

 undoubtedly one which in most experimental cases would 

 demand long period for the effectiveness of its tests. 



"We need not expect mutilations to become transmis- 

 sible, nor most of the responses established during the 

 life-time of an individual; but this in no w T ay precludes 

 the possibility for life-time responses which are con- 

 tinued for generations, or which may happen to strike a 

 race at some plastic period of its existence. 



12 In the adoption of a new habit during the life-time an adaptive char- 

 acter may appear from generation to generation as the habit comes to be 

 assumed, and give the appearance of being transmissible, whereas it may he 

 formed as an ordinary response to the new stimuli. Especially where an 

 animal is in process of changing the stimuli to which it is subject will it 

 often be difficult to distinguish a transmissible from a responsive adaptive 



"Morgan, T. II., "Evolution and Adaption," 1903, p. 230. 



