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THE AMERICAN NATURALIST [Vol. LI 



the underside of leaves, it was suggested that the orienta- 

 tion of the young might depend upon the force of gravity, 

 but eggs that were first marked with India ink and then 

 placed in every conceivable position with respect to grav- 

 ity proceeded to develop as though undisturbed.^"* It 

 seemed from this, therefore, that the position of the young 

 must be predetermined in the undeveloped egg. 



Several kinds of experiments were performed in order 

 to discover the complexity and fixity of this apparent 

 organization. First, the eggs were subjected to a force 

 greater than gravity by means 

 of a centrifugal machine. Hun- 

 dreds of eggs were revolved at 

 different rates of speed for vari- 

 ous lengths of time and in many 

 different positions. A description 

 of one experiment will serve to 

 illustrate the results obtained.^ ^ 

 In this experiment freshly laid 

 eggs were placed in cavities in 

 a block of paraffin with the pos- 

 terior end toward the center of 

 I'otation, and were revolved in a 

 liydi-nnlic contvifuge for sixteen 



