You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <images imcontinue="1|Chemical_structure.jpg" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Main Page">
        <images>
          <im ns="6" title="File:Actual brain.jpg" />
          <im ns="6" title="File:Analogies example.jpg" />
          <im ns="6" title="File:Arguments sun faces.jpg" />
          <im ns="6" title="File:Awarepath multiextension 1.jpg" />
          <im ns="6" title="File:Blue butterfly.jpg" />
          <im ns="6" title="File:Book worm.jpg" />
          <im ns="6" title="File:BrainImage.jpg" />
          <im ns="6" title="File:Brain circuits.jpg" />
          <im ns="6" title="File:Brain magnifying glass.jpg" />
          <im ns="6" title="File:Chem-lab saal uni-leipzig brockhaus.jpg" />
        </images>
      </page>
    </pages>
  </query>
</api>