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THE POPULAR SCIENCE MONTHLY 



account, verified by Winter, the protoplasm of the microsphseric indi- 

 vidual breaks down into .small fragments, eacli fragment enclosing a 

 number of these granules of chromatin, which coalesce later to form one 

 single nucleus. If we accept Lister's account the coalescence occurs 

 before the breaking down of the protoplasmic mass. All observers 

 agree, however, that hundreds of minute nucleated " embryos " arise 



Photograph by J. J. Lister. 

 Fig. 7. Polystomella crispa. Liberation of pseudo-podiospores 

 from the megalosphaeric individual. 



by fragmentation of the parent protoplasm (Fig. 7). The breaking 

 down of the original nuclei is an important step, for by this process the 

 important germ plasm is formed, which in the finely granular state 

 described was named by Hertwig the chromidia. 



The small " embryos " leave the parent organism in swarms 

 (Fig. 8), and the calcareous shell is finally deserted. Each " embryo " 

 then grows into a megalosphaeric or large-chambered individual in 

 which the primary nucleus remains single for a considerable period. 

 New chambers are formed about the primary central chamber and a 

 new adult individual results from the continued growth. The history 

 of the nucleus, however, is quite different from that of the microsphasric 

 individual. The protoplasm contains a large primary nucleus which 

 ultimately degenerates and disappears. During life of the individual, 

 however, this nucleus gives rise by chromatin " secretion " or by frag- 

 mentation, to an immense number of minute nuclei which are dis- 

 tributed throughout the protoplasmic mass. Each nucleus becomes 



