diff --git a/panda/src/chan/animControl.I b/panda/src/chan/animControl.I
index 0d04cf4cdd..63df29f07f 100644
--- a/panda/src/chan/animControl.I
+++ b/panda/src/chan/animControl.I
@@ -116,8 +116,15 @@ get_anim() const {
 
 ////////////////////////////////////////////////////////////////////
 //     Function: AnimControl::get_channel_index
-//       Access: Public
-//  Description:
+//       Access: Published
+//  Description: Returns the particular channel index associated with
+//               this AnimControl.  This channel index is the slot on
+//               which each AnimGroup is bound to its associated
+//               PartGroup, for each joint in the animation.
+//
+//               It will be true that
+//               get_part()->find_child("n")->get_bound(get_channel_index())
+//               == get_anim()->find_child("n"), for each joint "n".
 ////////////////////////////////////////////////////////////////////
 INLINE int AnimControl::
 get_channel_index() const {
diff --git a/panda/src/chan/animControl.h b/panda/src/chan/animControl.h
index 49f3fed179..125de0e2fa 100644
--- a/panda/src/chan/animControl.h
+++ b/panda/src/chan/animControl.h
@@ -73,6 +73,7 @@ PUBLISHED:
 
   PartBundle *get_part() const;
   INLINE AnimBundle *get_anim() const;
+  INLINE int get_channel_index() const;
 
   void output(ostream &out) const;
 
@@ -86,8 +87,6 @@ public:
   bool channel_has_changed(AnimChannelBase *channel) const;
   void mark_channels();
 
-  INLINE int get_channel_index() const;
-
 private:
 
   enum ActionType {
diff --git a/panda/src/chan/movingPartBase.I b/panda/src/chan/movingPartBase.I
index 808c5bed44..229a22b35b 100644
--- a/panda/src/chan/movingPartBase.I
+++ b/panda/src/chan/movingPartBase.I
@@ -29,3 +29,37 @@ MovingPartBase(const MovingPartBase &copy) :
 {
   // We don't copy the bound channels.
 }
+
+////////////////////////////////////////////////////////////////////
+//     Function: MovingPartBase::get_max_bound
+//       Access: Published
+//  Description: Returns the number of channels that might be bound to
+//               this PartGroup.  This might not be the actual number
+//               of channels, since there might be holes in the list;
+//               it is one more than the index number of the highest
+//               bound channel.  Thus, it is called get_max_bound()
+//               instead of get_num_bound().
+////////////////////////////////////////////////////////////////////
+INLINE int MovingPartBase::
+get_max_bound() const {
+  return _channels.size();
+}
+
+////////////////////////////////////////////////////////////////////
+//     Function: MovingPartBase::get_bound
+//       Access: Published
+//  Description: Returns the nth bound channel on this PartGroup.  n
+//               can be determined by iterating from 0 to one less
+//               than get_max_bound(); or n might be
+//               AnimControl::get_channel_index().
+//
+//               This will return NULL if there is no channel bound on
+//               the indicated index.  It is an error to call this if
+//               n is less than zero or greater than or equal to
+//               get_max_bound().
+////////////////////////////////////////////////////////////////////
+INLINE AnimChannelBase *MovingPartBase::
+get_bound(int n) const {
+  nassertr(n >= 0 && n < (int)_channels.size(), NULL);
+  return _channels[n];
+}
diff --git a/panda/src/chan/movingPartBase.cxx b/panda/src/chan/movingPartBase.cxx
index 42b986f461..18e14ddb08 100644
--- a/panda/src/chan/movingPartBase.cxx
+++ b/panda/src/chan/movingPartBase.cxx
@@ -208,6 +208,10 @@ pick_channel_index(plist<int> &holes, int &next) const {
 ////////////////////////////////////////////////////////////////////
 void MovingPartBase::
 bind_hierarchy(AnimGroup *anim, int channel_index) {
+  if (chan_cat.is_debug()) {
+    chan_cat.debug()
+      << "binding " << *this << " to " << *anim << "\n";
+  }
   while ((int)_channels.size() <= channel_index) {
     _channels.push_back((AnimChannelBase*)0L);
   }
diff --git a/panda/src/chan/movingPartBase.h b/panda/src/chan/movingPartBase.h
index 5ce05383a5..6ac1cbd98a 100644
--- a/panda/src/chan/movingPartBase.h
+++ b/panda/src/chan/movingPartBase.h
@@ -42,6 +42,11 @@ protected:
 public:
   MovingPartBase(PartGroup *parent, const string &name);
 
+PUBLISHED:
+  INLINE int get_max_bound() const;
+  INLINE AnimChannelBase *get_bound(int n) const;
+
+public:
   virtual TypeHandle get_value_type() const=0;
   virtual AnimChannelBase *make_initial_channel() const=0;
   virtual void write(ostream &out, int indent_level) const;
diff --git a/panda/src/chan/partGroup.cxx b/panda/src/chan/partGroup.cxx
index 0d015c14f0..67fb72c735 100644
--- a/panda/src/chan/partGroup.cxx
+++ b/panda/src/chan/partGroup.cxx
@@ -168,7 +168,7 @@ public:
 ////////////////////////////////////////////////////////////////////
 void PartGroup::
 sort_descendants() {
-  sort(_children.begin(), _children.end(), PartGroupAlphabeticalOrder());
+  stable_sort(_children.begin(), _children.end(), PartGroupAlphabeticalOrder());
 
   Children::iterator ci;
   for (ci = _children.begin(); ci != _children.end(); ++ci) {