206 The Unitij of the Organism 



of the entire ^gg. It is therefore the power [of such a part] 

 to develop the entire organism." ^ 



The meaning of "prosi^ective significance" is that "each 

 blastomere is a function of its position in the whole." ^ 



The extreme form of Driesch's view is set forth in his 

 lucid and often quoted statement that the early cells of 

 the sea-urchin embryo are "composed of an indifferent ma- 

 terial, so that they may be thrown about at will, like balls 

 in a pile, without the least impairment of their power of 

 development." ^ 



Balancing the Account Beti&een the Mosaic and Totipotence 



Theories 



Every one, it would appear, must then admit that, so far 

 as concerns the part of the cell- theory which would see in 

 the cell the "key" to all development, these discoveries by 

 Roux and Driesch neutralize each other. If the cells of 

 the frog's egg seem in their individual capacities to produce 

 each its particular part of the organism, those of the sea- 

 urchin's egg seem, with equal positiveness, to do nothing of 

 the sort, but on the contrary to be entirely subject to the 

 needs of the future organism. This, I say, is manifestly the 

 effect which the original discoveries of Roux and Driesch 

 have upon each other. But later researches have undoubt- 

 edly proved that more animals resemble the sea-urchin than 

 the frog so far as the developmental attribute is concerned. 

 And the case of Triton, the near relative of the frog should 

 be particularly remembered. "There is no necessity," says 

 Herlitzka, "for a predisposition of various parts of the 

 isolated blastomere (or of the egg) to give origin to de- 

 terminate organs." ^" 



It is quite impossible and unnecessary to follow all the 

 details of the Rouxian and Drieschian views of the relation 

 of cells to the organism in development ; but we must notice 



