diff --git a/js/fea/dmaCell.js b/js/fea/dmaCell.js
index 96ad164fa8e316844dc44bc908ffced651f51cbf..7eb85b92740ed9e1a56610769746d4bbf91f4a67 100644
--- a/js/fea/dmaCell.js
+++ b/js/fea/dmaCell.js
@@ -91,11 +91,10 @@
     };
 
     DMACell.prototype.drawForMode = function(mode){
-        position = this.position;
         if (mode == "cell"){
             if (this.cellMesh) this._setCellMeshVisibility(true);
             else {
-                this.cellMesh = this._buildCellMesh(position);
+                this.cellMesh = this._buildCellMesh(this.position);
                 window.three.sceneAdd(this.cellMesh);
             }
         } else if (mode == "parts"){
diff --git a/js/models/lattice.js b/js/models/lattice.js
index 0b9c35a642d6acc22204a2ecec14e70c14956f2f..db09d1cd65c6cce9a72865fb16f5591c17a4010b 100644
--- a/js/models/lattice.js
+++ b/js/models/lattice.js
@@ -159,15 +159,8 @@ Lattice = Backbone.Model.extend({
     },
 
     clearCells: function(){
-        _.each(this.get("cells"), function(cellLayer){
-            _.each(cellLayer, function(cellCol){
-                _.each(cellCol, function(cell){
-                    if (cell) {
-                        cell.remove();
-                    }
-                });
-            });
-
+        this._iterCells(this.get("cells"), function(cell){
+            if (cell) cell.remove();
         });
         this.set("cells", this.defaults.cells);
         this.set("numCells", 0);
@@ -176,10 +169,21 @@ Lattice = Backbone.Model.extend({
 
     _cellModeDidChange: function(){
         var mode = this.get("cellMode");
-        _.each(this.get("cells"), function(cell){
-            if (cell.drawForMode) cell.drawForMode(mode);
+        this._iterCells(this.get("cells"), function(cell){
+            if (cell && cell.drawForMode) cell.drawForMode(mode);
         });
         window.three.render();
+    },
+
+    _iterCells: function(cells, callback, vars){
+        _.each(cells, function(cellLayer){
+            _.each(cellLayer, function(cellColumn){
+                _.each(cellColumn, function(cell){
+                    callback(cell);
+                });
+            });
+
+        });
     }
 
 });
\ No newline at end of file