260 



growth of the personal structure of the body, which he terms 

 somatic cells ; the other for the ultimate perpetuation of the 

 species or hlaMogenic cells which pass on as it were from genera- 

 tion to generation. 



Further, it has been shown by previous writers that the above- 

 mentioned particulate body or pronucleus arising out of the 

 fusion of elements from both parents, is really formed by the 

 conjugation of the nuclei, or more accurately, of certain parts of 

 the nuclei, of the respective reproductive cells male and female. 

 80 it must be that it is the nuclear substance which is the real 

 bearer of hereditary tendencies and much has been written lately 

 as to the intricate structure of the nuclei of active cells. The 

 two nuclei must be supposed not only to carry over germ-plasm 

 from each immediate parent, but also some fraction from every 

 preceding parent, the amount diminishing in geometrical ratio 

 as we proceed backwards in the ancestral line. 



This is Weismann's main contention briefly stated, but in 

 order fully to understand his train of reasoning, and to realise 

 the full foixe of his conclusions, it is necessary to review some 

 other of his facts and arguments which are so intricately bound 

 up with his central theory of heredity as to make the compre- 

 hension of them a necessary preliminary to the consideration of 

 the main issue. 



Starting from the position that all living organisms, whether 

 plants or animals, consist of one or more cells, we may class 

 them in two great divisions — unicellular and multicellular. The 

 unicellular plants and animals are termed Protophyta and Pro- 

 tozoa, the multicellular Metaphyta and Metazoa respectively, and 

 it is hardly necessary to point out that it is the unicellular plants, 

 and animals which exhibit the phenomena of life in the simplest 

 and most elementary forms. Recognising the well-known facts 

 that the unicellular organisms reproduce themselves by fission, 

 that is, by the division of the parent organism into two approxi- 

 mately equal parts, or by the closely analogous process of gem- 

 mation, in which a small bud of the parent tissue grows from the 

 body to increase in size and to be subsequently separated into an 

 independent individual, Professor Weismann comes to the some- 

 what startling conclusion, which seems to have been overlooked 

 by other biologists, that aboriginally life is immortal, and that 

 the conclusion, that death is necessarily the end of all living 

 things, must be abandoned. For, when a simple unicellular 

 organism, such as the Amoeba, reproduces its kind, it does so by 

 this process of fission or division into two equal parts, each half 

 growing into a Protozoon resembling its parent, and thus the 

 actual and identical protoplasm of the parent Amoeba lives on, as 

 it were, in the bodies of its descendants, each one of which con- 



