160 TVe Unity of the Organism. 



structure which wc see in a cell-mosaic is something super- 

 added to organization, not itself the foundation of organi- 

 zation." Tlien follows this pregnant sentence : "Compara- 

 tive embryology reminds us at every turn that the organism 

 dominates cell formation, using for the same purpose one, 

 several, or many cells, massing its material and directing 

 its movements, and shaping its organs, as if cells did not 

 exist, or as if they existed only in complete subordination to 

 its will, if I may so speak." ^'^ After sketching the rise and 

 fall of that ])uzzling structure in many vertebrate embryos 

 known as Kupffer's vesicle, Whitman writes: "This re- 

 markable reproduction of a form-phase that is to last only 

 a few hours and then pass away without leaving a visible 

 trace of its existence, cannot be explained as due to cell- 

 foi'mation nor as the result of iiuUiyichutl action or inter- 

 action on the part of the cells. The embryonic mass acts 

 rather as a tinit, tending always to assume the form peculiar 

 to the state of development reached by its essential 'archi- 

 tectonic elements,' (Briicke), elements that are no less real 

 because, like the atom and molecule, they are too minute to 

 be seen by the aid of our present microscopes. That cells 

 as such do not participate in this formative act, is shown 

 by the mode of development of the vesicle and by the absence 

 of cells in its ventral and lateral wall." ^^ '-- 



We have now examined Whitman's position far enough 

 for our ])resent point; that, namely, of showing the strength 

 of his conviction that cells taken individually furnish no 

 adequate explanation of the normally developing individual 

 organism. The evidence he presents to this end never has 

 been nor, I am persuaded, can ever be overpowered. On the 

 other hand, any one who will study, as Whitman himself 

 says, "more faithfully the living embryo during its forma- 

 tion" ^' will find abundance of further evidence to the same 

 effect. So far — and this is a very long way — Whitman was 

 crystal clear. Further than this he was unable to break away 



