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>
    <alltransclusions gatcontinue="Bildinformation|131" />
  </query-continue>
  <query>
    <pages>
      <page pageid="73" ns="6" title="Datei:Skirrow.jpg" />
      <page pageid="129" ns="6" title="Datei:Hygswitch100.png" />
      <page pageid="130" ns="6" title="Datei:Mayweather100.png" />
      <page pageid="375" ns="0" title="Albernian Space Agency" />
      <page pageid="389" ns="0" title="Keep Medea clean &amp; healthy" />
      <page pageid="449" ns="0" title="Llyngwyn" />
      <page pageid="450" ns="0" title="Nessie Dyce" />
      <page pageid="451" ns="0" title="Ei Bendith ar ei Ben" />
      <page pageid="452" ns="0" title="Albernian Empire Society" />
      <page pageid="454" ns="0" title="Liste der Regenten von Llyngwyn" />
    </pages>
  </query>
</api>