What is not revealed by the x-ray is why the artist made the changes.

Some theories exist on the subject. One suggests that his change of heart was due to the fact that he could not satisfactorily finish the image of the figure (MacGregor was not a renowned figure painter) so decided the impact of a bold, painterly still life would be far greater.

 

References
The Glasgow Boys. The Glasgow School of Painting 1875-1895. Roger Bylcliffe, John Murray Publishers Ltd, London 1985. pp. 72-77

Radiography of Cultural Material. Janet Lang and Andrew Middleton. Butterworth-Heinmann 2nd edition 2005