THEORY OF THE DEVELOPMENT OF ORGANISMS 115 



quite different. We must regard the functions of 

 a cell that is part of an organism, disregarding 

 external influences, as determined by the whole 

 organism, and only by the cell itself, in so far as 

 that forms a greater or less part of the whole 

 organism. When not part of an organism, the cell 

 is independent, and entirely determines its own 

 function. Nowhere is it easier than in this case to 

 confuse possibilities with facts, and nowhere is the 

 confusion more fatal. From a morphological point 

 of view, one may confidently regard the cell as an 

 individual ; but it must be borne in mind that an 

 abstraction has been made. Physiologically con- 

 sidered, the cell is an individual only when it is 

 isolated from a complex and is independent ; of 

 this no abstraction can be made/ 



According to the conception I have been explain- 

 ing, cells merge their independent individuality in 

 that of the whole, and so the force that directs 

 their ultimate development, and that leads to their 

 appropriate elaboration, cannot be within them, 

 cannot reside in special groups of determinants, 

 in the sense of Weismann. It is given by the 

 relations in which the cells come to stand to the 

 whole organism and to the various parts of the 

 organism, and, on the other hand, to surrounding- 

 things. Naturally, such relations differ with the 

 place or position occupied by cells in the whole 

 organism, and in this way there come to be in- 

 numerable conditions making for diverging direc- 

 tions of development, for division of labour, and 

 for dissimilar, histological differentiation. The 



