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="BdT|8593" />
  </query-continue>
  <query>
    <pages>
      <page pageid="8582" ns="0" title="Bild des Tages 12. Januar" />
      <page pageid="8584" ns="0" title="Bild des Tages 5. April" />
      <page pageid="8585" ns="0" title="Bild des Tages 29. April" />
      <page pageid="8586" ns="0" title="Bild des Tages 23. Juli" />
      <page pageid="8587" ns="0" title="Bild des Tages 16. Oktober" />
      <page pageid="8588" ns="0" title="Bild des Tages 9. Februar" />
      <page pageid="8589" ns="0" title="Bild des Tages 4. Mai" />
      <page pageid="8590" ns="0" title="Bild des Tages 28. Mai" />
      <page pageid="8591" ns="0" title="Bild des Tages 21. August" />
      <page pageid="8592" ns="0" title="Bild des Tages 14. November" />
    </pages>
  </query>
</api>