54 THE BIOLOGICAL PROBLEM OF TO-DAY 



normal situation, the induced organs conform to 

 the specific type in all respects, and indicate that 

 all the cells of an organism contain, as the result 

 of doubling division, the characters of germinal 

 rudiments of the whole organism. On the other 

 hand, heteromorphoses bear heavily against the 

 doctrine of determinants. For it is impossible that, 

 in the architecture of the germplasm, there can be 

 provision, in the form of special determinants, for 

 events so foreign to the natural course of develop- 

 ment as these arbitrary, outer stimulants. 



Heteromorphosis may be extended to include 

 more than Loeb intended by reckoning under it 

 artificially-produced modification of the early stages 

 in the cleavage of the egg. I have in mind those 

 experiments by Driesch, Wilson, and myself, in 

 which the first cells of the embryonic history were 

 induced to form parts of the embryo, to which in 

 the normal course they would not have given rise. 

 In these cases heteromorphosis begins from the 

 first cleavage of the egg. 



In an ingenious way Driesch compressed fer- 

 tilised echinoderm eggs between glass plates, and 

 so secured that the first sixteen cells were separated, 

 not by alternate vertical and horizontal planes, as 

 in the normal development, but only by vertical 

 planes. In the resulting one-layered plate of cells 

 the nuclei had relative positions quite different 

 from the normal. As, notwithstanding this, the 

 distorted eggs developed into normal plutei larvae, 

 Driesch inferred that the cell material composing 

 the earliest cells of echinoids is equivalent in all 



