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="Anna_Monroe_and_HEQ.jpg" />
  </query-continue>
  <query>
    <pages>
      <page pageid="150" ns="6" title="File:1978 Summer.jpg" />
      <page pageid="234" ns="6" title="File:4Cousins.jpg" />
      <page pageid="218" ns="6" title="File:Aaron (Arkadiy) Smushkevich.JPG" />
      <page pageid="221" ns="6" title="File:Aaron (Arkadiy) Smushkevich on left.JPG" />
      <page pageid="220" ns="6" title="File:Aaron (Arkadiy) Smushkevich on right.JPG" />
      <page pageid="217" ns="6" title="File:Abraham Smushkevich and Freida.JPG" />
      <page pageid="216" ns="6" title="File:Abraham Smushkevich undated.JPG" />
      <page pageid="342" ns="6" title="File:Achille Deledda.JPG" />
      <page pageid="319" ns="6" title="File:Allison.jpg" />
      <page pageid="356" ns="6" title="File:Andrea Ruffinu.JPG" />
    </pages>
  </query>
</api>