140 ON VARIABILITY AND ADAPTATION 



transmission of acquired characters does not wholly accord 

 with medical experience, we may well ask : can we gain a con- 

 ception of the intimate nature of inheritance which is in accord 

 with that experience ? 



Inheritance True and False. — My only regret is that, in 

 striving to gain that conception, I shall have to inflict upon 

 you yet another theory ; my only apology, that that theory does 

 appear to satisfy the conditions met with in man. First, how- 

 ever, it is necessary to lay down clearly what is not inheritance, 

 for in medical writings and in ordinary medical parlance a terrible 

 confusion prevails upon this point, and much that is certainly 

 not inherited is commonly spoken of as being hereditary. There 

 is, for example, no such thing as hereditary syphilis. There 

 is congenital syphilis, and there are, to employ Founder's term, 

 inherited " parasyphilitic " lesions, but " hereditary " and 

 " congenital " are not and must not be regarded as interchange- 

 able terms. 



The confusion is due to the common error of regarding the 

 individual as beginning his existence at the moment of birth 

 and not until then, so that everything occurring before that 

 moment is grouped in one category, everything after in another. 

 The chick, so to speak, is not a chick until it breaks open the 

 shell ; its status from the moment it ceases to be a new-laid 

 egg — or, more strictly, the egg of commerce — until it emerges 

 from the shell is not recognized in law, and fresh egg and chick 

 are commodities of wholly different orders. But the individual 

 existence of the chicken has already begun even before the egg 

 is laid, and what is true of the chick is equally true of the human 

 being. The individual begins the moment that fecundation is 

 accomplished, the moment that nuclear material of the sperma- 

 tozoon fuses with the nuclear material of the ovum and these 

 twain become one. Compared with the event, birth is seen to 

 be of secondary importance, for the intra-uterine association of 

 the embryo with the maternal tissues is but one means employed 

 by a restricted number of species to ensure the satisfactory 

 nourishment of the individual during the earlier stages of develop- 

 ment. The recognition of these facts is essential for any serious 

 study of the problems of human inheritance. Any disturbance 

 due to influences affecting the individual from without while 

 in utero is acquired. It certainly must not be spoken of as 



