THE REAL DIFFICULTY 205 



Nor does the fact that morbid processes in a particular part 

 may result in a diffusion of toxins, which saturate even the germ- 

 cells, help us much in our attempt to picture how a modification 

 could become transmissible. For there is not the slightest 

 reason for supposing that the ordinary modifications in which 

 naturalists are interested, which experimental evolutionists can 

 bring about, are associated with the formation of specific toxins 

 which might diffuse through the whole system. 



Spencer's Statement of the a priori Argument. — As Herbert Spencer 

 was perhaps the keenest and most convinced upholder of the affirma- 

 tive position, it seems just to give his statement of the a priori 

 argument. We have made a comment on each of the steps. 



(1) "That changes of structure caused by changes of action 



must be transmitted, however obscurely, appears to be 

 a deduction from first principles — or if not a specific 

 deduction, still, a general implication." 



"For if an organism, A, has, by any peculiar habit or 

 condition of life, been modified into the Form A 1 , it follows 

 that all the functions of A 1 , reproductive function included, 

 must be in some degree different from the functions of A." 



"An organism being a combination of rhythmically 

 acting parts in moving equilibrium, the action and structure 

 of any one part cannot be altered without causing altera- 

 tions of action and structure in all the rest." 

 Comment. — (a) It is not denied that some deeply saturating 

 modifications of the body, affecting the nutritive stream, 

 may affect the reproductive organs. This is not the point 

 at issue, (b) How far a modification is likely to affect the 

 reproductive organs must be determined by observation 

 and experiment. The appreciability of the change will 

 depend on the amount and nature of the modification, 

 and on the intimacy of the correlation subsisting in the 

 organism. Dislodging a rock may alter the centre of 

 gravity of the earth, but it does not do so appreciably. 



(2) " And if the organism A, when changed to A 1 , must be changed 



in all its functions, then the offspring of A 1 cannot be the 



same as they would have been had it retained the form A." 



Comment. — This is logical, but is it true ? The change from 



A to A 1 may be important, it may appreciably alter the 



