Z2>6 THE GRAMMAR OF SCIENCE 



into the phenomenal world, and then rather oddly states 

 that they compel us to suspend all physical conceptions, 

 has, on the other hand, shown good reason for Darwin's 

 theory not being valid as a full description of the pheno- 

 mena of heredity, notably because the transmission of 

 acquired characteristics receives support from that theory, 

 but hardly from our perceptual experience. He has in 

 his turn endeavoured to formulate a theory which shall 

 more accurately describe the facts of heredity, especially 

 those relating to the non-transmission of characters ac- 

 quired by parents, owing either to use or accident during 

 their lives. This theory is summed up in the formula of 

 the " continuity of the germ-plasm." According to this 

 theory there exists a substance of a definite cJieviical and 

 molecular stnicturc termed germ -plasm, which resides 

 somewhere in the germ-cells, from which reproduction 

 takes place. In each reproduction a part of the germ- 

 plasm " contained in the parent egg-cell is not used up 

 in the construction of the body of the offspring, but is 

 reserved unchanged for the formation of the germ-cells of 

 the following generation." This constitutes the continuity 

 of the germ-plasm.-' Variation arises from the mixture 

 of parental germ-plasms ; similarity of characteristics in 

 parent and offspring — inheritance — from their both being 

 developed under the control of the same germ-plasm. 

 The " immortal " j^art of the organism which descends 

 from generation to generation is the germ-plasm.^ Now 

 this hypothesis of Weismann as a conceptual mode 

 of describing our perceptual experience seems to be of 

 considerable value, but the author weakens his position 

 throughout by projecting his conceptions into the pheno- 

 menal world, where up to the present nothing has been 

 identified as the perceptual equivalent of germ-plasm. 



1 The reader must be careful to note that it is not a continuity of the 

 germ-cells, but of a hitherto unidentified substance contained in these cells. 

 Cells, we know, nuclei we know, with complicated networks of nucleoli ; 

 but what is gerf/i-plasin ? Something not to be seen and not to be caught by 

 aniline stain or acetic acid. 



2 The Coutiuuity of the Germ-plasm as the Foundation of a Theory of 

 Heredity, 1885. Essays o]i Heredity, pp. 165-248. 



