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>
    <allfileusages gafcontinue="Belief_System5.jpg" />
  </query-continue>
  <query>
    <pages>
      <page pageid="34257" ns="6" title="File:Baby genius.jpg" />
      <page pageid="34470" ns="6" title="File:Baby mutants.jpg" />
      <page pageid="34248" ns="6" title="File:Baby thinking.jpg" />
      <page pageid="33618" ns="6" title="File:Bat.jpg" />
      <page pageid="33578" ns="6" title="File:Bat and centipede.jpg" />
      <page pageid="33575" ns="6" title="File:Bee.jpg" />
      <page pageid="34244" ns="6" title="File:Bees.jpg" />
      <page pageid="34124" ns="6" title="File:Belief System.jpg" />
      <page pageid="34123" ns="6" title="File:Belief System1.jpg" />
      <page pageid="34122" ns="6" title="File:Belief System3.jpg" />
    </pages>
  </query>
</api>