Statement of Weismanns System (1886). 11 



We have come, then, to these results. Proto- 

 plasm was originally immortal, barring accidents ; 

 and it still continues to be immortal in the case of 

 unicellular organisms which propagate a-sexually. 

 But in the case of all multicellular organisms, which 

 propagate sexually, natural selection has reduced 

 the term of life within the smallest limits that in 

 each given case are compatible with the performance 

 of the sexual act and the subsequent rearing of pro- 

 geny — reserving, however, the original endowment 

 of immortality for the germinal elements, whereby 

 a continuum of life has been secured from the earliest 

 appearance of life until the present day. 



Now, in view of these results the question arises, — 

 Why should the sexual methods of propagation have 

 become so general, if their effect has been that of 

 determining the necessary death of all individuals 

 presenting them ? Why, in the course of organic 

 evolution, should these newer methods have been 

 imposed on all the higher organisms, when the conse- 

 quence is that all these higher organisms must pay 

 for the innovation with their lives ? Weismann's 

 answer to this question is as interesting and ingenious 

 as all that has gone before. Seeing that sexual pro- 

 pagation is so general as to be practically universal 

 among multicellular organisms, it is obvious that in 

 some way or another it must have had a most important 

 part to play in the general scheme of organic evolution. 

 What, then, is the part that it does play? What is 

 its raison detre ? Briefly, according to Weismann, its 

 function is that of furnishing congenital variations to 

 the ever-watchful agency of natural selection, in order 

 that natural selection may always preserve the most 



