diff --git a/eo/src/eoGenOp.h b/eo/src/eoGenOp.h
index a8143a9e..b24dad7d 100644
--- a/eo/src/eoGenOp.h
+++ b/eo/src/eoGenOp.h
@@ -48,6 +48,8 @@ the original population, is an instantiation of the next population and
 has often a selection function embedded in it to select new individuals.
 
 Note that the actual work is performed in the apply function.
+AND that the apply function is responsible for invalidating 
+the object if necessary
  */
 template <class EOT>
 class eoGenOp : public eoOp<EOT>, public eoUF<eoPopulator<EOT> &, void>
diff --git a/eo/src/eoInvalidateOps.h b/eo/src/eoInvalidateOps.h
index f3a3b4cb..4643c727 100644
--- a/eo/src/eoInvalidateOps.h
+++ b/eo/src/eoInvalidateOps.h
@@ -37,6 +37,9 @@ the return type of the operator and invalidate the fitness of the individual.
 This functor is used in algorithms that work with straight eoMonOp, eoBinOp
 or eoQuadOp operators, for instance eoSGA. Note that eoGenOp derived operators
 generally do invalidate the fitness of the objects they have changed.
+
+Return value means "Has_Changed" and not "Needs_To_Be_Invalidated"
+as successive invalidation are not really a problem
 */
 
 template <class EOT>
@@ -68,6 +71,9 @@ the return type of the operator and invalidate the fitness of the individual.
 This functor is used in algorithms that work with straight eoMonOp, eoBinOp
 or eoQuadOp operators, for instance eoSGA. Note that eoGenOp derived operators
 generally do invalidate the fitness of the objects they have changed.
+
+Return value means "Has_Changed" and not "Needs_To_Be_Invalidated"
+as successive invalidation are not really a problem
 */
 
 template <class EOT>
@@ -99,6 +105,9 @@ the return type of the operator and invalidate the fitness of the individual.
 This functor is used in algorithms that work with straight eoMonOp, eoBinOp
 or eoQuadOp operators, for instance eoSGA. Note that eoGenOp derived operators
 generally do invalidate the fitness of the objects they have changed.
+
+Return value means "Has_Changed" and not "Needs_To_Be_Invalidated"
+as successive invalidation are not really a problem
 */
 
 template <class EOT>
diff --git a/eo/src/eoProportionalCombinedOp.h b/eo/src/eoProportionalCombinedOp.h
index b36c1d2c..5fba7fe5 100644
--- a/eo/src/eoProportionalCombinedOp.h
+++ b/eo/src/eoProportionalCombinedOp.h
@@ -205,6 +205,6 @@ std::vector<double> rates;
 };
 
 
-// for General Ops, it's another story - 
+// for General Ops, it's another story - see eoOpCOntainer
 #endif
 
diff --git a/eo/src/eoSGATransform.h b/eo/src/eoSGATransform.h
index e06aad6d..47e2747a 100644
--- a/eo/src/eoSGATransform.h
+++ b/eo/src/eoSGATransform.h
@@ -84,9 +84,9 @@ template<class EOT> class eoSGATransform : public eoTransform<EOT>
   };
     
  private:
-  eoQuadOp<EOT>& cross;
+  eoInvalidateQuadOp<EOT> cross;
   double crossoverProba;
-  eoMonOp<EOT>& mutate;
+  eoInvalidateMonOp<EOT> mutate;
   double mutationProba;
 };
 
diff --git a/eo/src/es/eoEsStdevXOver.h b/eo/src/es/eoEsStdevXOver.h
index c13adf6e..be5071e7 100644
--- a/eo/src/es/eoEsStdevXOver.h
+++ b/eo/src/es/eoEsStdevXOver.h
@@ -55,14 +55,7 @@ public :
     bool objectChanged = objectXOver(_eo1, _eo2); // as vector<double>
     bool stdDevChanged = stdDevXOver(_eo1.stdevs, _eo2.stdevs);
 
-    /// Marc, I didn't change it, but if only the stdev has changed,
-    /// doesn't that mean that the fitness is stil valid. Maarten
-    if ( objectChanged || stdDevChanged )
-      {
-        return true;
-      }
-
-    return false;
+    return objectChanged;
   }
 
 private: