ON THE NATURE OF CELL-ORGANIZATION. 103 



significance, 1 due to physiological causes, I believe, emanating 

 from the fundamental difference existing between the chromo- 

 some and the cytoplasm, the difference between the two 

 being of such a character that makes their mutual association 

 necessary for the existence of each. The chromosome 

 cannot grow beyond a certain bulk, nor is the cytoplasm 

 capable of unlimited growth, without each meeting with 

 restraining influence from the other, if one may express it in 

 a metaphorical way. The formation of a nucleated cell is, 

 in other words, a secondary adaptation to keep the nuclear and 

 cytoplasmic material within the reach of reciprocal physiologi- 

 cal influence of each. The division of the cell, when such exists, 

 is the result incidental to the increase in the number of two 

 kinds of cell-forming organisms existing in each nucleated cell. 



The sphere within which the symbiotic reciprocal influence of 

 these two cell-forming organisms is felt, corresponds to what 

 Sachs 2 calls the encrgid. The term cncrgid as a substitute for 

 the modern idea of the nucleated cell, aptly expresses one 

 aspect of the cell-organism, namely, its physiological side. 

 From the genetic standpoint, as given in the present paper, 

 this single energid is already a complex of at least two kinds 

 of organisms, different in their anatomical character, in their 

 function, and in their origin. 



Stated in this way, the view is not a new one, but agrees, in 

 its broadest feature, with the idea of a cell expressed by 

 Darwin in his theory of Pangenesis, 3 and in its special aspect 

 which considers mutualistic symbiosis as the basis of cellular 

 organization, may perhaps add a more concrete meaning to his 

 well-known passage, without necessarily adopting his further 

 inference from it, when he said that "an organic being is a 

 microcosm a little universe, formed of a host of self-propa- 

 gating organisms inconceivably minute and numerous as the 

 stars in the heavens." 



1 Sachs: Lectures on the Physiology of Plants, p. 73. 



2 Julius v. Sachs: Physiologische Notizen II. Beitrdge zur Zellentheorie. Flora: 

 Jahrg. 75, 1892. Reprinted in his Gesammeltc Abhandlungen, //., 1893, pp. 1 150- 



"55- 



8 Darwin: Provisional Hypothesis of Pangenesis (Animals and Plants under 

 Domestication, vol. ii.); The Descent of Man, Appleton, p. 228. 



