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parts upon the i»iferiorIj integrating parts of the brain. Yet the brain 

 volumes, corresponding to equal body weights, of heteroneuric species 

 are to each other as J to 2, 3 or 4, which implies that the volume 

 of those superposed chains of cells, in the origination of a heteroneuric 

 species, is equal to, double or triple the vohnne of the preexisting 

 chains. We may infer from this, tluü the phylogenetic progress of 

 the brain, by evident discontinuous variation (mutation), after all 

 depends on segregation of aliquot parts from polyploidly increased 

 nuclear substance. 



As, again, the size of the nerve cell body and its chief component 

 parts is adjusted to the mechanism of the whole animal, and every 

 nerve cell is bound to cooperation with many homologous, 

 and non-homologous nerve cells, its relatively stable character, 

 manifested in the ontogenetically limited, and phylogenetically in- 

 frequently, but then from the beginning definitely increased multi- 

 plication by division, becomes comprehensible, especially when — 

 in the origination of a heteroneuric species — the multiplication 

 must be greater in the most compounded and intricately functionating 

 parts of the brain. 



