Drag and drop issue in Jquery

Drag and drop issue in Jquery

I am trying to create a feature that can drag table cell from 1 table to
another table cell.
My request is when user drag the cell from table 1 to table 2. The table 1
cell will still have the same texts remaining in the cell. My codes can do
that. However, when the user drag cells in table 2. I want the dragged
cell text disappear.
For example
<table class='table'>
<tr>
<td>drag1</td>
<td>drag2</td>
</tr>
<tr>
<td>drag3</td>
<td>drag4</td>
</tr>
</table>
<br/>
<table class='table'>
<tr>
<td></td>
<td></td>
</tr>
<tr>
<td></td>
<td></td>
</tr>
</table>
user can drag drag1 from table 1 to table 2 and drag1 still remain in table1
<table class='table'>
<tr>
<td>drag1</td>
<td>drag2</td>
</tr>
<tr>
<td>drag3</td>
<td>drag4</td>
</tr>
</table>
<br/>
<table class='table'>
<tr>
<td>drag1</td>
<td></td>
</tr>
<tr>
<td></td>
<td></td>
</tr>
</table>
but if user drag cell in table 2, drag1 will disappear and relocate to
another cell
<table class='table'>
<tr>
<td>drag1</td>
<td>drag2</td>
</tr>
<tr>
<td>drag3</td>
<td>drag4</td>
</tr>
</table>
<br/>
<table class='table'>
<tr>
<td></td>
<td>drag1</td>
</tr>
<tr>
<td></td>
<td></td>
</tr>
</table>
I can't change table classname nor giving a id. so it's a bit tough.
Here is my jsfiddle
http://jsfiddle.net/7Xd6n/6/
Thanks for the help!