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>
    <allcategories accontinue="フェニキア" />
  </query-continue>
  <query>
    <allcategories>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">ウガリット神話</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">エラム</c>
      <c size="4" pages="4" files="0" subcats="0" xml:space="preserve">ギリシア神話</c>
      <c size="2" pages="2" files="0" subcats="0" xml:space="preserve">ケルト神話</c>
      <c size="2" pages="2" files="0" subcats="0" xml:space="preserve">コロン</c>
      <c size="13" pages="13" files="0" subcats="0" xml:space="preserve">シュメール神話</c>
      <c size="2" pages="2" files="0" subcats="0" xml:space="preserve">ゾロアスター教</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">ヒッタイト</c>
      <c size="4" pages="4" files="0" subcats="0" xml:space="preserve">ヒッタイト神話</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">ヒンドゥー教</c>
    </allcategories>
  </query>
</api>