OA' THE XATURE OF CELL-ORGANIZATION. loi 



Any theory that explains the nature of a nucleated cell 

 must explain all of these, and hold them under one common 

 point of view. Such a theory luiist, in short, recognize not only 

 the profoiDid physiological interdependence betzveen nucleus and 

 cytoplasm, but it must also recognize their natural motphological 

 independoice. 



The doctrine of symbiosis, first propounded b)- De Bary,^ 

 just fulfils these requirements, inasmuch as it means now, in a 

 more restricted sense, the normal felloivship or the cojisortiai 

 union of tivo or more organisms of dissimilar origin, each of 

 li'Jiich acts as the physiological compliment to the other in the 

 struggle for existence. 



Under the assumption of such a principle as that of 

 mutualistic symbiosis, the fact of natural anatomical difference 

 between the chromosome and the cytoplasm can only be har- 

 monized with the fact of their complimentary physiological 

 adaptation. Only on the assumption that the chromosome and 

 cytoplasm had dissimilar origin, can we understand their 

 constant difference in optical, microchemical and anatomical 

 characters, through all phases of their activity. 



To summarize for the sake of clearness, then, the general 

 consequence of the symbiotic existence to its participants, we 

 may say, that, (i) inasmuch as one organic being comes in 

 connection with another in order to be nourished and nourish 

 the other in return, they obtain a freedom in the choice of 

 dwelling place, which is not enjoyed by them otherwise; (2) 

 symbiosis of two dissimilar organisms induces certain modifi- 

 cation in each symbiont, by the suppression of certain 

 characters originally present in each, or by the acquisition of 

 others, which were formerly absent; (3) when the adaptation 

 of one symbiont to the other becomes perfect, the whole 

 community behaves like a new organism, subject to new laws 

 of growth and of development, and is no longer subjected to 

 those relating to each symbiont separately, and thus, (4) a 

 power of adaptation to the external world which each symbiont 

 did not possess individually, in the struggle for existence, may 

 be acquired indirectly, by the combined efforts of the two. (5) 



^ De ]-5ary : Die Erscheinwig dcr Symbiose. Strassburg, 1S79. 



