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="05._Philistia_Kline,_Ailene,_Hazel,,_Don,Annie_Sheffer,_Bernard-1.jpg" />
  </query-continue>
  <query>
    <pages>
      <page pageid="6174" ns="6" title="File:003A Henry Kline farm site lane.jpg" />
      <page pageid="6175" ns="6" title="File:009a Henry Kline farm site, cleared land overgrown.jpg" />
      <page pageid="6176" ns="6" title="File:013A Henry Kline farm site, stone wall.jpg" />
      <page pageid="6177" ns="6" title="File:015A Henry Kline farm site, stone wall.jpg" />
      <page pageid="6178" ns="6" title="File:017A Henry Kline farm site, rock pile.jpg" />
      <page pageid="6179" ns="6" title="File:021A Henry Kline farm site, rock pile.jpg" />
      <page pageid="4709" ns="6" title="File:02 Mrs Weller &amp; Philistia Kline, postcard front.jpg" />
      <page pageid="4710" ns="6" title="File:02 Mrs Weller &amp; Philistia Kline, postcard message.jpg" />
      <page pageid="2615" ns="6" title="File:03SL Minta Dittman.JPG" />
      <page pageid="4460" ns="6" title="File:03 OZ Robert Beals.jpg" />
    </pages>
  </query>
</api>