I02 BIOLOGICAL LECTURES. 



In proportion as the symbiotic adaptation of two or more 

 organisms becomes more and more perfect, each symbiont 

 loses the power of living independently which it originally 

 possessed. 



The view that ascribes a symbiotic significance to the 

 association of these two different kinds of cell-forming 

 organisms in each cell, explains the following points, viz., (I) 

 the constant difference in anatomical, optical and micro-chemi- 

 cal characteristics between the chromosome and the cytoplasm; 

 (II) the maintenance of their specific identity through all 

 phases of developmental changes, as caryokinesis and fecunda- 

 tion; (III) the participation of both nucleus and cytoplasm in 

 the manifestation of non-developmental phenomena of cell- 

 life, such as secretion, excretion, etc. ; (IV) the interchange of 

 metabolic products between nucleus and cytoplasm as the 

 necessary outcome of a symbiotic mode of existence; (V) the 

 reason why the cytoplasm separated from the nucleus, or the 

 nucleus isolated from the cytoplasm invariably perishes; and, 

 therefore, (VI) why the nucleus and cytoplasm are the j^hysio- 

 logical organs of a cell, and yet they are not organs from a 

 morphological or developmental standpoint. 



The nuclear substance must not be considered, in any sense, 

 as inactive, which becomes only active when it migrates into 

 the cytoplasm as Hugo de Vries^ maintains in his well-known 

 work. The nuclear substance of a cell is just as much active 

 as the cytoplasm, according to the present view, but in an 

 entllf-ely different manner, somewhat in the same way as the 

 chlorophyll-bearing algal cells and the colorless fungal elements 

 in a lichen are active at the same time, but each in its own way. 



The vital properties of a cell do not reside in the nucleus 

 alone, nor in the cytoplasm which surrounds it, but in the two 

 together. The cell maybe destitute of a cell-wall — cytotlieca 

 — or each may be enclosed within its own cell-membrane, or a 

 cell may exist side by side without any visible boundary 

 between them — the syncytium. The division of an organism 

 into distinct cell -entities in a multicellular organism is a 

 phenomenon widely distributed, it is true, but still of secondary 



1 Hugo de \'ries: hitraidlulare Pangenesis, Jena, 1SS9. 



