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>
    <allimages gaicontinue="Before_TheBall03_50.jpg" />
  </query-continue>
  <query>
    <pages>
      <page pageid="160" ns="6" title="File:After TheBall.jpg" />
      <page pageid="38" ns="6" title="File:After TheBall02 85 - Copy.jpg" />
      <page pageid="122" ns="6" title="File:After TheBall03 50.jpg.jpg" />
      <page pageid="40" ns="6" title="File:After TheBall04 50.jpg" />
      <page pageid="155" ns="6" title="File:B After TheBall04 50.jpg" />
      <page pageid="154" ns="6" title="File:B Before TheBall03 50.jpg" />
      <page pageid="156" ns="6" title="File:B ColorChange TheBall06 50.jpg" />
      <page pageid="159" ns="6" title="File:Before TheBall.jpg" />
      <page pageid="37" ns="6" title="File:Before TheBall01 85 - Copy.jpg" />
      <page pageid="121" ns="6" title="File:Before TheBall02 50.jpg.jpg" />
    </pages>
  </query>
</api>