THE PRESENT EVOLUTION OF MAN — PHYSICAL 243 



of it. Here, then, the Lamarkian theory breaks down 

 utterly. 



Conformably then to the a priori conclusion which 

 we have already arrived at, namely, that the germ cell, 

 a unicellular organism, is not, and cannot possibly be, so 

 modified by the changes in the other unicellular organ- 

 isms with which it is associated, the somatic cells, that, 

 when it proliferates, it reproduces a cell-community 

 composed of its descendants, in which those changes 

 are reproduced, — i. c. conformably to the a priori 

 conclusion that the acquired traits of multicellular 

 organisms are not, and cannot possibly be, transmissible, 

 — we have no alternative but to believe that races which 

 have long been afflicted by a deadly and prevalent 

 disease are more resistant to it than races which have 

 not been so afflicted, or have been less afflicted, solely 

 because in the presence of tlie disease the survival of the 

 fittest and the elimination of the Imfittest has resulted 

 in an evolution, first, of the inborn power of making 

 resistance ; and second, of the inborn power of acquiring 

 capabilities for making resistance — powers which to 

 some extent have been developed generally by Natural 

 Selection in all higher multicellular organisms, in con- 

 sequence of their liability to become the prey of low 

 parasitic unicellular organisms, but which, in the 

 presence of any particular zymotic disease, undergo a 

 further evolution in a particular direction. 



Here it is necessary to enter into a digression. 

 Because some zymotic diseases — e.g. syphilis and 

 tuberculosis — are under certain circumstances trans- 

 missible from the parent to the offspring, it has often 

 and triumphantly been held, that a proof is thereby 

 afforded of the transmissibility of acquired traits. 

 Such arguments, however, afford proof of great con- 

 fusion of ideas only. The microbes and toxins of any 

 zymotic disease which may afflict an individual are not 



