anchor.diff:      }), {
       maxzoom: gridmaxzoom,
       interactivity: options.interactivity === false ? false : 'id',
  +    interactionsURL: intereactionsServer( ) + gridTileSuffix,
       disabled: options.disabled
     });
     pointLayer = this.addTileLayer( _.map( tileservers , function( base ) {
  
positive.code:     interactivity: options.interactivity === false ? false : 'id',
      minzoom: gridmaxzoom + 1,
      gridminzoom: gridmaxzoom + 1,
      disabled: options.disabled
    })
    // add a toggle for this layer to the overlay control, if it exists
  
negative.code:       interactivity = options.interactivity;
    if( options.interactivity ) {
      // windshaft needs the interactivity param to know what data to render
      var interactionsURLs = options.interactionsURL ?
        [ options.interactionsURL ] : tileURLs;
      options.grids = _.map( interactionsURLs, function( l ) {
        return google.maps.Map.prototype.interactivityURL( l, options.interactivity );
      })
    }
  