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="Pull-down-shematic-734px.jpg" />
  </query-continue>
  <query>
    <pages>
      <page pageid="6589" ns="6" title="File:1408789731 micro.JPG" />
      <page pageid="4164" ns="6" title="File:620px-Hexachlorobutadiene.svg.png" />
      <page pageid="4009" ns="6" title="File:Anti.gif" />
      <page pageid="9655" ns="6" title="File:Frequency Polygon.png" />
      <page pageid="3791" ns="6" title="File:Glaucoma-awareness-month.jpg" />
      <page pageid="5572" ns="6" title="File:Isovolrel.gif" />
      <page pageid="6591" ns="6" title="File:Nitrate test.png" />
      <page pageid="6339" ns="6" title="File:Phosp.gif" />
      <page pageid="9652" ns="6" title="File:Picture1.png" />
      <page pageid="3643" ns="6" title="File:ProteinExample.png" />
    </pages>
  </query>
</api>