Statement of Weismanris System (1886). 23 



particles of each must always remain the same, no 

 matter how many admixtures they may undergo 

 with particles of other materials, such as chalk, slate ; 

 &c. Now, inasmuch as it is an essential — because 

 a logically necessary — part of Weismann's theory 

 to assume such absolute stability or unchangeable- 

 ness on the part of germ-plasm, the question arises, 

 and has to be met, What was the origin of those 

 differences of character in the different germ-plasms 

 of multicellular organisms which first gave rise, and 

 still continue to give rise, to congenital variations 

 by their mixture one with another ? This important 

 question Weismann answers by supposing that these 

 differences originally arose out of the differences 

 in the unicellular organisms, which were the ancestors 

 of the primitive multicellular organisms. Now, as 

 before stated, different forms of unicellular organisms 

 are supposed to have originated as so many results of 

 differences in the direct action of the environment. 

 Consequently, according to the theory, all congenital 

 variations which now occur in multicellular organisms, 

 are really the distant results of variations that were 

 aboriginally induced in their unicellular ancestors by 

 the direct action of surrounding conditions of life. 



I think it will be well to conclude by briefly sum- 

 marising the main features of this elaborate theory. 



Living material is essentially, or of its own nature, 

 imperishable ; and it still continues to be so in the 

 case of unicellular organisms which propagate by 

 fission or gemmation. But as soon as these primitive 

 methods of propagation became, from whatever 

 cause, superseded by sexual, it ceased to be for the 

 benefit of species that their constituent individuals 



