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="Building|189" />
  </query-continue>
  <query>
    <pages>
      <page pageid="44" ns="0" title="Thunderhead Reach" />
      <page pageid="70" ns="0" title="Chambered Reef" />
      <page pageid="73" ns="0" title="Mogi Nest" />
      <page pageid="75" ns="0" title="Vapor Mahal" />
      <page pageid="97" ns="0" title="Magma Chamber" />
      <page pageid="130" ns="0" title="Underworld Gate" />
      <page pageid="132" ns="0" title="Ord Stone" />
      <page pageid="144" ns="0" title="Gossamer Palace" />
      <page pageid="179" ns="0" title="Bamboo Watch Tower" />
      <page pageid="186" ns="0" title="Emerald Spring" />
    </pages>
  </query>
</api>