THEORIES OF HEREDITY 7 



with inborn, and will be so used in the present work ; but by 

 medical men, especially, it is sometimes applied to traits which 

 appear before birth as distinguished from those which appear 

 afterwards. From the point of view of heredity, however, since 

 characters may be acquired in utero, the episode of birth is of 

 no importance. It is necessary to define these terms exactly, 

 for otherwise the most desperate confusion is apt to occur and 

 indeed has very often arisen. 1 Their importance is due to the 

 fact that, while it is admitted on all hands that inborn traits 

 (including variations) tend to descend from parents to off- 

 spring and to more remote descendants, it is now denied by 

 the vast majority of biologists that " modifications " are ever 

 inherited Thus, while it is admitted that if a man be blind 

 " by nature " his blindness will very probably descend to his 

 offspring, it is denied if he acquire blindness (as by injury, for 

 instance) that his defect will tend to be inherited. 



1 If once we apprehend clearly the fact that the difference between the 

 inborn and the acquired is one of origin we shall avoid many of the 

 grotesque errors which vitiate the writings of some popular authors who 

 have dealt with this subject. Even when heredity is discussed in medi- 

 cal meetings some one is pretty sure to remark with an air of finality, 

 " Acquired characters must be transmissible, for every character must 

 have had a beginning, and therefore must have been acquired origin- 

 ally." This sentence is such a triumph of inaccurate statement and 

 loose thought, and within its brief limits sets forth so neatly the principal 

 source of confusion prevalent in popular and medical terminology, that 

 it is worth while to examine it at length. It assumes that the difference 

 between the inborn and the acquired is not one of origin, but one of age, 

 and that, therefore, all old characters are inborn, and all new characters 

 are acquired. But language and bipedal locomotion are very old characters 

 in man : yet they remain acquirements, for every man still learns to 

 talk and walk. Acquired immunity against this or that disease is another 

 old character ; it also remains an acquirement, for every man who 

 acquires immunity acquires it afresh. On the other hand, to term a new 

 character an acquirement merely because it is new is an absurdity for 

 more reasons than one. In the first place the words " inborn " and 

 " acquired " are well-established technical terms with very precise and 

 definite meanings. Biologists use them to mark the vitally important 

 distinction between blastogenetic and somatogenetic characters. An 

 argument which is based on a misuse of terms does not commend itself as 

 conclusive from a scientific point of view. In the second place the dis- 

 tinction between the new and the old is, in this connection, a valueless one. 

 Every character is new to the individual who has it. Thus a man's 

 head is as new to him as a sixth digit or any other variation from the 

 parental type. In the third place the whole argument is beside the 

 mark, for the fact that some new characters are transmissible has never 

 been disputed. On the contrary, the fact that they are transmissible is the 

 corner-stone of every theory of heredity. It is admitted on all hands 

 that new inborn characters are transmissible new characters, that is, 

 which take origin in the germ-plasm. All that has ever been disputed 

 is that somatic modifications, whether new or old, are transmissible. 



