DEATH 



But as the distinguished zoologist has again taken up 

 his theory with energy in his instructive Lectures on the 

 Theory of the Descent (1902), and has added to it er- 

 roneous observations on the nature of death, I am 

 obliged to return to the point. Precisely because this 

 interesting work gives most valuable support to the 

 theory of evolution, and maintains Darwin's theory of 

 selection and its consequences with great effect, I feel it 

 is necessary to point out considerable weaknesses and 

 dangerous errors in it. The chief of these is the im- 

 portant theory of the germ-plasm and the consequent 

 opposition to the inheritance of acquired characteristics. 

 Weismann deduces from this a radical distinction be- 

 tween the unicellular and the multicellular organisms. 

 The latter alone are mortal, the former immortal; "be- 

 tween the unicellular and the multicellular lies the intro- 

 duction of physiological — that is to say, normal — death." 

 We must say, in opposition to this, that the physiological 

 individuals (bionta) among the protista are just as 

 limited in their duration as among the histona. But if 

 the chief stress in the question is laid, not on the in- 

 dividuality of the living matter, but on the continuity 

 of the metabolic life-movement through a series of 

 generations, it is just as correct to affirm a partial 

 immortality of the plasm for the multicellulars as for 

 the unicellulars. 



The immortality of the unicellulars, on which Weis- 

 mann has laid so much stress, can only be sustained 

 for a small part of the protists even in his own sense — 

 namely, for those which simply propagate by cleavage, 

 the chromacea and bacteria among the monera (chapter 

 ix.), the diatomes and paulotomes among the protophyta, 

 and a part of the infusoria and rhizopods among the 

 protozoa. Strictly speaking, the individual life is 

 destroyed when a cell splits into two daughter-cells. 

 One might reply with Weismann that in this case the 



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