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="ALK4.png" />
  </query-continue>
  <query>
    <pages>
      <page pageid="736" ns="6" title="File:2005-2010-comparison.jpeg" />
      <page pageid="560" ns="6" title="File:2008 Arctas anthro v1.2 07222009.zip.txt" />
      <page pageid="1116" ns="6" title="File:7 day time tests.png" />
      <page pageid="1306" ns="6" title="File:A3O2.png" />
      <page pageid="1304" ns="6" title="File:ACET.png" />
      <page pageid="1305" ns="6" title="File:ACTA.png" />
      <page pageid="411" ns="6" title="File:ACTA OH.png" />
      <page pageid="1307" ns="6" title="File:ALD2.png" />
      <page pageid="403" ns="6" title="File:ALD2 OH.png" />
      <page pageid="848" ns="6" title="File:ALD2 photolysis.png" />
    </pages>
  </query>
</api>