80 Mutations and Evolution. 



there is multiplication of free nuclei, 1 which arrange themselves in 

 a particular manner, but without the formation of cell walls until 

 later. That cells can develope within a cell is also well exemplified 

 in the development of the embryo-sac of Angiosperms. 



In the same year Whitman (1894), in a notable paper, attacked 

 the cell theory on fundamental theoretical grounds. He concluded 

 that the formation of the embryo is not controlled by the form of 

 the cleavage. " The plastic forces heed no cell-boundaries, but 

 mould the germ-mass regardless of the way it is cut up into cells." 

 His position was that "organization precedes cell-formation and 

 regulates it." 



It is impossible here to enter into a discussion of the various 

 views which grew out of the extensive studies on cell-lineage, but 

 granting the accuracy of the above limitations of the cell theory, it 

 will be seen that they are in no way out of harmony with the view of 

 mutations as cell variations, or rather nuclear variations, previously 

 expressed. Another limitation of the cell theory will be considered 

 in the next chapter. 



1 Incidentally it may be pointed out that any comprehensive theory of 

 heredity must be one which is applicable equally to those cases in which 

 regular cleavage of the egg takes place and those in which in one stage the 

 embryo contains free nuclei. Since the nuclei are the only structures in 

 common, and the laws of inheritance remain the same in both cases, ergo the 

 nuclei and not the planes of cleavage must determine those laws. 



