jquery - クローンを追加および削除しますか?

Question

小さな間違いを犯したに違いない。私が取り組んだjsfiddleがあります。追加ボタンと削除ボタンを機能させようとしています。

それらには、私が含めていない非表示と表示の要素もありますが、問題ではありませんか?

http://jsfiddle.net/27N7Y/

HTML:

<div class="question">
<div class="questiontext">
    23. Have you or anyone included in this application ever previously applied for a visa or travelled to Australia?
</div>
<div class="questionradioanswer">
    No <input type="radio" id="notravel" name="previousvisa" value="No" class="radiobutton">
    Yes <input type="radio" id="yestravel" name="previousvisa" value="Yes" class="radiobutton">
    </div>
    <div id="question23hide">
        Provide dates of previous visits to Australia<br>
        <select id="selectday6" class="daydate">
            <option>Day</option>
            <script>
                var select = document.getElementById("selectday6");
                var options = new Array();
                var temp = 1;
                for (var i = 0; i < 31; i++) {
                options.push(temp);
                temp++;
                }
                for (var i = 0; i < options.length; i++) {
                var opt = options[i];
                var el = document.createElement("option");
                el.textContent = opt;
                el.value = opt;
                select.appendChild(el);
                }
            </script>
        </select>
        <select id="selectmonth6" class="monthdate">
            <option>Month</option>
            <script>
                var select = document.getElementById("selectmonth6");
                var options = ["January", "Febuary", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
                for (var i = 0; i < options.length; i++) {
                var opt = options[i];
                var el = document.createElement("option");
                el.textContent = opt;
                el.value = opt;
                select.appendChild(el);
                }
            </script>
        </select>
        <select id="selectyear6" class="yeardate">
            <option>Year</option>
            <script>
                var select = document.getElementById("selectyear6");
                var options = new Array();
                var firstyear = (new Date().getFullYear()) - 18;
                var temp = firstyear;
                for (var i = 0; i < 83; i++) {
                options.push(temp);
                temp--;
                }
                for (var i = 0; i < options.length; i++) {
                var opt = options[i];
                var el = document.createElement("option");
                el.textContent = opt;
                el.value = opt;
                select.appendChild(el);
                }
            </script>
        </select>
        </div>
        <div id="adddeleteprevious">
            <div id="addprevious">
                <input type="button" class="button" value="Add Previous Visits">
                </div>
                <div id="deleteprevious">
                    <input type="button" class="button" value="Delete Previous Visits">
                    </div>
                </div>
            </div>

Jクエリ:

$("#addprevious").click(function(){
    $(".question23hide:last").after($(".question23hide:first").clone(true));
});

$("#deleteprevious").click(function() {
    if($(".question23hide").length!=1)
        $(".question23hide:last").remove();
});