THE WONDERS OF LIFE 



dividing unicellular organism lives on as a whole in its 

 offspring, and that we have no corpse, no dead remains 

 of the living matter, left behind. But that is not true 

 of the majority of the protozoa. In the highly devel- 

 oped ciliata the chief nucleus is lost, and there must be 

 from time to time a conjugation of two cells and a mutual 

 fertilization of their secondary nuclei, before there can 

 be any further multiplication by simple cleavage. How- 

 ever, in most of the sporozoa and rhizopoda, which 

 generally propagate by spore formation, only one por- 

 tion of the unicellular organism is used for this ; the other 

 portion dies, and forms a "corpse." In the large 

 rhizopods (thalamophora and radiolaria) the spore- 

 forming inner part, which lives on in the offspring, is 

 smaller than the decaying outer portion, which becomes 

 the corpse. 



Weismann's view of the secondary "introduction of 

 physiological death in the multicellulars" is just as 

 untenable as his theory of the immortality of the 

 unicellulars. According to this opinion, the death of the 

 histona — both the metaphyta and metazoa — is a pur- 

 posive outcome of adaptation, only introduced by se- 

 lection when the multicellular organism has reached a 

 certain stage of complexit}^ of structure, which is incom- 

 patible with its original immortalit}^ Natural selection 

 v\^ould thus kill the immortal and preserve only the 

 mortal ; it would interfere with the multiplication of the 

 immortals in the bloom of their years, and only use the 

 mortal for rearing posterity. The curious conclusions 

 which Weismann reached in developing this theory of 

 death, and the striking contradictions to his own theory 

 of the germ-plasm which he fell into, have been pointed 

 out by Kassowitz in the forty-ninth chapter of his Gen- 

 eral Biology. In my opinion, this paradoxical theory of 

 death has no more basis than the germ-plasm theory he 

 has ingeniously connected with it. We may admire the 



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