Page:George Archdall Reid 1896 The present evolution of man.djvu/255

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

Conformably then to the à 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 organisms 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.e. conformably to the a priori conclusion that the acquired traits of multicellular organisms are not, aud 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 the disease the survival of the fittest and the elimination of the unfittest 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 consequence 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 transmissible 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 confusion of ideas only. The microbes and toxins of any zymotic disease which may afflict an individual are not