Statement of Weismanris System (1886). 25 



that we recognize as congenital. Therefore, natural 

 selection has always to wait and to watch for such 

 variations of germ-plasm as will eventually prove 

 beneficial to the individuals developed therefrom, 

 who will then transmit this peculiar quality of germ- 

 plasm to their progeny, and so on. Therefore also — 

 and this is most important to remember — natural 

 selection as thus working becomes the one and only 

 cause of organic evolution in all the multicellular 

 organisms, just as the direct action of the environ- 

 ment is the one and only cause of it in the case 

 of all the unicellular organisms. But inasmuch as the 

 multicellular organisms were all in the first instance 

 derived from the unicellular, and inasmuch as their 

 germ-plasm is of so stable a nature that it can 

 never be altered by any agencies internal or external 

 to the organisms presenting it, it follows that all 

 congenital variations are the remote consequences 

 of aboriginal differences on the part of unicellular 

 ancestors. And, lastly, it follows also that these 

 congenital variations — although now so entirely in- 

 dependent of external conditions of life, and even of 

 activities internal to organisms themselves — were 

 originally and exclusively due to the direct action 

 of such conditions on the lives of their unicellular 

 ancestors; while even at the present day no one con- 

 genital variation can arise which is not ultimately 

 due to differences impressed upon the protoplasmic 

 substance of the germinal elements, when the parts 

 of which these are now composed constituted integral 

 parts of the protozoa, which were directly and differ- 

 entially affected by their converse with their several 

 environments. 



