diff --git a/src/mlpack/methods/ann/layer/base_layer.hpp b/src/mlpack/methods/ann/layer/base_layer.hpp
index 1b9f0d8b87..876d87e6f2 100644
--- a/src/mlpack/methods/ann/layer/base_layer.hpp
+++ b/src/mlpack/methods/ann/layer/base_layer.hpp
@@ -120,12 +120,12 @@ class BaseLayer
   }
 
   //! Get the input parameter.
-  InputDataType& InputParameter() const { return inputParameter; }
+  InputDataType const& InputParameter() const { return inputParameter; }
   //! Modify the input parameter.
   InputDataType& InputParameter() { return inputParameter; }
 
   //! Get the output parameter.
-  OutputDataType& OutputParameter() const { return outputParameter; }
+  OutputDataType const& OutputParameter() const { return outputParameter; }
   //! Modify the output parameter.
   OutputDataType& OutputParameter() { return outputParameter; }
 
@@ -133,6 +133,15 @@ class BaseLayer
   OutputDataType const& Delta() const { return delta; }
   //! Modify the delta.
   OutputDataType& Delta() { return delta; }
+  
+  /**
+   * Serialize the layer.
+   */
+  template<typename Archive>
+  void Serialize(Archive& /* ar */, const unsigned int /* version */)
+  {
+    /* Nothing to do here */
+  }
 
  private:
   //! Locally-stored delta object.
diff --git a/src/mlpack/methods/ann/layer/bias_layer.hpp b/src/mlpack/methods/ann/layer/bias_layer.hpp
index 11d293d2a7..10b8b90436 100644
--- a/src/mlpack/methods/ann/layer/bias_layer.hpp
+++ b/src/mlpack/methods/ann/layer/bias_layer.hpp
@@ -123,29 +123,39 @@ class BiasLayer
   }
 
   //! Get the weights.
-  InputDataType& Weights() const { return weights; }
+  InputDataType const& Weights() const { return weights; }
   //! Modify the weights.
   InputDataType& Weights() { return weights; }
 
   //! Get the input parameter.
-  InputDataType& InputParameter() const { return inputParameter; }
+  InputDataType const& InputParameter() const { return inputParameter; }
   //! Modify the input parameter.
   InputDataType& InputParameter() { return inputParameter; }
 
   //! Get the output parameter.
-  OutputDataType& OutputParameter() const { return outputParameter; }
+  OutputDataType const& OutputParameter() const { return outputParameter; }
   //! Modify the output parameter.
   OutputDataType& OutputParameter() { return outputParameter; }
 
   //! Get the delta.
-  OutputDataType& Delta() const { return delta; }
+  OutputDataType const& Delta() const { return delta; }
   //! Modify the delta.
   OutputDataType& Delta() { return delta; }
 
   //! Get the gradient.
-  InputDataType& Gradient() const { return gradient; }
+  InputDataType const& Gradient() const { return gradient; }
   //! Modify the gradient.
   InputDataType& Gradient() { return gradient; }
+  
+  /**
+   * Serialize the layer.
+   */
+  template<typename Archive>
+  void Serialize(Archive& ar, const unsigned int /* version */)
+  {
+    ar & data::CreateNVP(weights, "weights");
+    ar & CreateNVP(bias, "bias");
+  }
 
  private:
   //! Locally-stored number of output units.
diff --git a/src/mlpack/methods/ann/layer/binary_classification_layer.hpp b/src/mlpack/methods/ann/layer/binary_classification_layer.hpp
index ae5fb46aee..368c1ecda9 100644
--- a/src/mlpack/methods/ann/layer/binary_classification_layer.hpp
+++ b/src/mlpack/methods/ann/layer/binary_classification_layer.hpp
@@ -60,6 +60,15 @@ class BinaryClassificationLayer
     for (size_t i = 0; i < output.n_elem; i++)
       output(i) = output(i) > 0.5 ? 1 : 0;
   }
+  
+  /**
+   * Serialize the layer.
+   */
+  template<typename Archive>
+  void Serialize(Archive& /* ar */, const unsigned int /* version */)
+  {
+    /* Nothing to do here */
+  }
 }; // class BinaryClassificationLayer
 
 //! Layer traits for the binary class classification layer.
diff --git a/src/mlpack/methods/ann/layer/conv_layer.hpp b/src/mlpack/methods/ann/layer/conv_layer.hpp
index 91c090315d..aeb6c07093 100644
--- a/src/mlpack/methods/ann/layer/conv_layer.hpp
+++ b/src/mlpack/methods/ann/layer/conv_layer.hpp
@@ -160,29 +160,46 @@ class ConvLayer
   }
 
   //! Get the weights.
-  OutputDataType& Weights() const { return weights; }
+  OutputDataType const& Weights() const { return weights; }
   //! Modify the weights.
   OutputDataType& Weights() { return weights; }
 
   //! Get the input parameter.
-  InputDataType& InputParameter() const { return inputParameter; }
+  InputDataType const& InputParameter() const { return inputParameter; }
   //! Modify the input parameter.
   InputDataType& InputParameter() { return inputParameter; }
 
   //! Get the output parameter.
-  OutputDataType& OutputParameter() const { return outputParameter; }
+  OutputDataType const& OutputParameter() const { return outputParameter; }
   //! Modify the output parameter.
   OutputDataType& OutputParameter() { return outputParameter; }
 
   //! Get the delta.
-  OutputDataType& Delta() const { return delta; }
+  OutputDataType const& Delta() const { return delta; }
   //! Modify the delta.
   OutputDataType& Delta() { return delta; }
 
   //! Get the gradient.
-  OutputDataType& Gradient() const { return gradient; }
+  OutputDataType const& Gradient() const { return gradient; }
   //! Modify the gradient.
   OutputDataType& Gradient() { return gradient; }
+  
+  /**
+   * Serialize the layer.
+   */
+  template<typename Archive>
+  void Serialize(Archive& ar, const unsigned int /* version */)
+  {
+    ar & data::CreateNVP(weights, "weights");
+    ar & data::CreateNVP(wfilter, "wfilter");
+    ar & data::CreateNVP(hfilter, "hfilter");
+    ar & data::CreateNVP(inMaps, "inMaps");
+    ar & data::CreateNVP(outMaps, "outMaps");
+    ar & data::CreateNVP(xStride, "xStride");
+    ar & data::CreateNVP(yStride, "yStride");
+    ar & data::CreateNVP(wPad, "wPad");
+    ar & data::CreateNVP(hPad, "hPad");
+  }
 
  private:
   /*
diff --git a/src/mlpack/methods/ann/layer/dropout_layer.hpp b/src/mlpack/methods/ann/layer/dropout_layer.hpp
index c9da7216a0..05d38c6915 100644
--- a/src/mlpack/methods/ann/layer/dropout_layer.hpp
+++ b/src/mlpack/methods/ann/layer/dropout_layer.hpp
@@ -147,17 +147,17 @@ class DropoutLayer
   }
 
   //! Get the input parameter.
-  InputDataType& InputParameter() const { return inputParameter; }
+  InputDataType const& InputParameter() const { return inputParameter; }
   //! Modify the input parameter.
   InputDataType& InputParameter() { return inputParameter; }
 
   //! Get the output parameter.
-  OutputDataType& OutputParameter() const { return outputParameter; }
+  OutputDataType const& OutputParameter() const { return outputParameter; }
   //! Modify the output parameter.
   OutputDataType& OutputParameter() { return outputParameter; }
 
   //! Get the detla.
-  OutputDataType& Delta() const { return delta; }
+  OutputDataType const& Delta() const { return delta; }
   //! Modify the delta.
   OutputDataType& Delta() { return delta; }
 
@@ -180,6 +180,16 @@ class DropoutLayer
   bool Rescale() const {return rescale; }
   //! Modify the value of the rescale parameter.
   bool& Rescale() {return rescale; }
+  
+  /**
+   * Serialize the layer.
+   */
+  template<typename Archive>
+  void Serialize(Archive& ar, const unsigned int /* version */)
+  {
+    ar & data::CreateNVP(ratio, "ratio");
+    ar & data::CreateNVP(rescale, "rescale");
+  }
 
  private:
   //! Locally-stored delta object.
diff --git a/src/mlpack/methods/ann/layer/linear_layer.hpp b/src/mlpack/methods/ann/layer/linear_layer.hpp
index 1c3a1fa60c..b34e978c36 100644
--- a/src/mlpack/methods/ann/layer/linear_layer.hpp
+++ b/src/mlpack/methods/ann/layer/linear_layer.hpp
@@ -111,29 +111,38 @@ class LinearLayer
   }
 
   //! Get the weights.
-  OutputDataType& Weights() const { return weights; }
+  OutputDataType const& Weights() const { return weights; }
   //! Modify the weights.
   OutputDataType& Weights() { return weights; }
 
   //! Get the input parameter.
-  InputDataType& InputParameter() const { return inputParameter; }
+  InputDataType const& InputParameter() const { return inputParameter; }
   //! Modify the input parameter.
   InputDataType& InputParameter() { return inputParameter; }
 
   //! Get the output parameter.
-  OutputDataType& OutputParameter() const { return outputParameter; }
+  OutputDataType const& OutputParameter() const { return outputParameter; }
   //! Modify the output parameter.
   OutputDataType& OutputParameter() { return outputParameter; }
 
   //! Get the delta.
-  OutputDataType& Delta() const { return delta; }
+  OutputDataType const& Delta() const { return delta; }
   //! Modify the delta.
   OutputDataType& Delta() { return delta; }
 
   //! Get the gradient.
-  OutputDataType& Gradient() const { return gradient; }
+  OutputDataType const& Gradient() const { return gradient; }
   //! Modify the gradient.
   OutputDataType& Gradient() { return gradient; }
+  
+  /**
+   * Serialize the layer
+   */
+  template<typename Archive>
+  void Serialize(Archive& ar, const unsigned int /* version */)
+  {
+    ar & data::CreateNVP(weights, "weights");
+  }
 
  private:
    /*
diff --git a/src/mlpack/methods/ann/layer/lstm_layer.hpp b/src/mlpack/methods/ann/layer/lstm_layer.hpp
index ee57456346..59c103c15a 100644
--- a/src/mlpack/methods/ann/layer/lstm_layer.hpp
+++ b/src/mlpack/methods/ann/layer/lstm_layer.hpp
@@ -248,27 +248,27 @@ class LSTMLayer
   }
 
   //! Get the peephole weights.
-  OutputDataType& Weights() const { return peepholeWeights; }
+  OutputDataType const& Weights() const { return peepholeWeights; }
   //! Modify the peephole weights.
   OutputDataType& Weights() { return peepholeWeights; }
 
   //! Get the input parameter.
-  InputDataType& InputParameter() const { return inputParameter; }
+  InputDataType const& InputParameter() const { return inputParameter; }
   //! Modify the input parameter.
   InputDataType& InputParameter() { return inputParameter; }
 
   //! Get the output parameter.
-  OutputDataType& OutputParameter() const { return outputParameter; }
+  OutputDataType const& OutputParameter() const { return outputParameter; }
   //! Modify the output parameter.
   OutputDataType& OutputParameter() { return outputParameter; }
 
   //! Get the delta.
-  OutputDataType& Delta() const { return delta; }
+  OutputDataType const& Delta() const { return delta; }
   //! Modify the delta.
   OutputDataType& Delta() { return delta; }
 
   //! Get the peephole gradient.
-  OutputDataType& Gradient() const { return peepholeGradient; }
+  OutputDataType const& Gradient() const { return peepholeGradient; }
   //! Modify the peephole gradient.
   OutputDataType& Gradient() { return peepholeGradient; }
 
@@ -276,6 +276,26 @@ class LSTMLayer
   size_t SeqLen() const { return seqLen; }
   //! Modify the sequence length.
   size_t& SeqLen() { return seqLen; }
+  
+  /**
+   * Serialize the layer.
+   */
+  template<typename Archive>
+  void Serialize(Archive& ar, const unsigned int /* version */)
+  {
+    ar & data::CreateNVP(peepholes, "peepholes");
+
+    if (peepholes)
+    {
+      ar & data::CreateNVP(peepholeWeights, "peepholeWeights");
+
+      if (Archive::is_loading::value)
+      {
+        peepholeDerivatives = arma::zeros<OutputDataType>(
+            peepholeWeights.n_rows, 3);
+      }
+    }
+  }
 
  private:
   //! Locally-stored number of output units.
diff --git a/src/mlpack/methods/ann/layer/one_hot_layer.hpp b/src/mlpack/methods/ann/layer/one_hot_layer.hpp
index a4dc6f4360..34458c3b2d 100644
--- a/src/mlpack/methods/ann/layer/one_hot_layer.hpp
+++ b/src/mlpack/methods/ann/layer/one_hot_layer.hpp
@@ -64,11 +64,12 @@ class OneHotLayer
   }
   
   /**
-   * Serialize the layer
+   * Serialize the layer.
    */
   template<typename Archive>
-  void Serialize(Archive& ar, const unsigned int /* version */)
-  {    			
+  void Serialize(Archive& /* ar */, const unsigned int /* version */)
+  {
+    /* Nothing to do here */
   }
 }; // class OneHotLayer
 
diff --git a/src/mlpack/methods/ann/layer/pooling_layer.hpp b/src/mlpack/methods/ann/layer/pooling_layer.hpp
index 64add9b1d3..e19ddceff2 100644
--- a/src/mlpack/methods/ann/layer/pooling_layer.hpp
+++ b/src/mlpack/methods/ann/layer/pooling_layer.hpp
@@ -133,26 +133,28 @@ class PoolingLayer
   }
 
   //! Get the input parameter.
-  InputDataType& InputParameter() const { return inputParameter; }
+  InputDataType const& InputParameter() const { return inputParameter; }
   //! Modify the input parameter.
   InputDataType& InputParameter() { return inputParameter; }
 
   //! Get the output parameter.
-  InputDataType& OutputParameter() const { return outputParameter; }
+  InputDataType const& OutputParameter() const { return outputParameter; }
   //! Modify the output parameter.
   InputDataType& OutputParameter() { return outputParameter; }
 
   //! Get the delta.
-  OutputDataType& Delta() const { return delta; }
+  OutputDataType const& Delta() const { return delta; }
   //! Modify the delta.
   OutputDataType& Delta() { return delta; }
   
   /**
-   * Serialize the layer
+   * Serialize the layer.
    */
   template<typename Archive>
   void Serialize(Archive& ar, const unsigned int /* version */)
-  {    			
+  {
+    ar & data::CreateNVP(kSize, "kSize");
+    ar & data::CreateNVP(pooling, "pooling");
   }
 
  private:
diff --git a/src/mlpack/methods/ann/layer/recurrent_layer.hpp b/src/mlpack/methods/ann/layer/recurrent_layer.hpp
index 729179f7ed..639852eedc 100644
--- a/src/mlpack/methods/ann/layer/recurrent_layer.hpp
+++ b/src/mlpack/methods/ann/layer/recurrent_layer.hpp
@@ -100,34 +100,44 @@ class RecurrentLayer
   }
 
   //! Get the weights.
-  OutputDataType& Weights() const { return weights; }
+  OutputDataType const& Weights() const { return weights; }
   //! Modify the weights.
   OutputDataType& Weights() { return weights; }
 
   //! Get the input parameter.
-  InputDataType& InputParameter() const { return inputParameter; }
+  InputDataType const& InputParameter() const { return inputParameter; }
   //! Modify the input parameter.
   InputDataType& InputParameter() { return inputParameter; }
 
   //! Get the input parameter.
-  InputDataType& RecurrentParameter() const { return recurrentParameter; }
+  InputDataType const& RecurrentParameter() const { return recurrentParameter; }
   //! Modify the input parameter.
   InputDataType& RecurrentParameter() { return recurrentParameter; }
 
   //! Get the output parameter.
-  OutputDataType& OutputParameter() const { return outputParameter; }
+  OutputDataType const& OutputParameter() const { return outputParameter; }
   //! Modify the output parameter.
   OutputDataType& OutputParameter() { return outputParameter; }
 
   //! Get the delta.
-  OutputDataType& Delta() const { return delta; }
+  OutputDataType const& Delta() const { return delta; }
   //! Modify the delta.
   OutputDataType& Delta() { return delta; }
 
   //! Get the gradient.
-  OutputDataType& Gradient() const { return gradient; }
+  OutputDataType const& Gradient() const { return gradient; }
   //! Modify the gradient.
   OutputDataType& Gradient() { return gradient; }
+  
+  /**
+   * Serialize the layer.
+   */
+  template<typename Archive>
+  void Serialize(Archive& ar, const unsigned int /* version */)
+  {
+    ar & data::CreateNVP(recurrentParameter, "recurrentParameter");
+    ar & data::CreateNVP(weights, "weights");
+  }
 
  private:
   //! Locally-stored number of input units.
diff --git a/src/mlpack/methods/ann/layer/softmax_layer.hpp b/src/mlpack/methods/ann/layer/softmax_layer.hpp
index 4bfd27d64e..151ebfef41 100644
--- a/src/mlpack/methods/ann/layer/softmax_layer.hpp
+++ b/src/mlpack/methods/ann/layer/softmax_layer.hpp
@@ -69,19 +69,28 @@ class SoftmaxLayer
   }
 
   //! Get the input parameter.
-  InputDataType& InputParameter() const { return inputParameter; }
+  InputDataType const& InputParameter() const { return inputParameter; }
   //! Modify the input parameter.
   InputDataType& InputParameter() { return inputParameter; }
 
   //! Get the output parameter.
-  OutputDataType& OutputParameter() const { return outputParameter; }
+  OutputDataType const& OutputParameter() const { return outputParameter; }
   //! Modify the output parameter.
   OutputDataType& OutputParameter() { return outputParameter; }
 
   //! Get the delta.
-  InputDataType& Delta() const { return delta; }
+  InputDataType const& Delta() const { return delta; }
   //! Modify the delta.
   InputDataType& Delta() { return delta; }
+  
+  /**
+   * Serialize the layer.
+   */
+  template<typename Archive>
+  void Serialize(Archive& /* ar */, const unsigned int /* version */)
+  {
+    /* Nothing to do here */
+  }
 
  private:
   //! Locally-stored delta object.
diff --git a/src/mlpack/methods/ann/layer/sparse_bias_layer.hpp b/src/mlpack/methods/ann/layer/sparse_bias_layer.hpp
index 8fc33c378e..9b79536e5c 100644
--- a/src/mlpack/methods/ann/layer/sparse_bias_layer.hpp
+++ b/src/mlpack/methods/ann/layer/sparse_bias_layer.hpp
@@ -116,6 +116,16 @@ class SparseBiasLayer
   InputDataType const& Gradient() const { return gradient; }
   //! Modify the gradient.
   InputDataType& Gradient() { return gradient; }
+  
+  /**
+   * Serialize the layer.
+   */
+  template<typename Archive>
+  void Serialize(Archive& ar, const unsigned int /* version */)
+  {
+    ar & data::CreateNVP(weights, "weights");
+    ar & data::CreateNVP(batchSize, "batchSize");
+  }
 
  private:
   //! Locally-stored number of output units.
diff --git a/src/mlpack/methods/ann/layer/sparse_input_layer.hpp b/src/mlpack/methods/ann/layer/sparse_input_layer.hpp
index 9b5f27474a..ce5ce7dc8e 100644
--- a/src/mlpack/methods/ann/layer/sparse_input_layer.hpp
+++ b/src/mlpack/methods/ann/layer/sparse_input_layer.hpp
@@ -114,9 +114,19 @@ class SparseInputLayer
   OutputDataType& Delta() { return delta; }
 
   //! Get the gradient.
-  OutputDataType& Gradient() const { return gradient; }
+  OutputDataType const& Gradient() const { return gradient; }
   //! Modify the gradient.
   OutputDataType& Gradient() { return gradient; }
+  
+  /**
+   * Serialize the layer.
+   */
+  template<typename Archive>
+  void Serialize(Archive& ar, const unsigned int /* version */)
+  {
+    ar & data::CreateNVP(weights, "weights");
+    ar & data::CreateNVP(lambda, "lambda");
+  }
 
  private:
   //! Locally-stored number of input units.
diff --git a/src/mlpack/methods/ann/layer/sparse_output_layer.hpp b/src/mlpack/methods/ann/layer/sparse_output_layer.hpp
index ae1597fafb..3022e2a17a 100644
--- a/src/mlpack/methods/ann/layer/sparse_output_layer.hpp
+++ b/src/mlpack/methods/ann/layer/sparse_output_layer.hpp
@@ -155,6 +155,18 @@ class SparseOutputLayer
   OutputDataType const& Gradient() const { return gradient; }
   //! Modify the gradient.
   OutputDataType& Gradient() { return gradient; }
+  
+  /**
+   * Serialize the layer.
+   */
+  template<typename Archive>
+  void Serialize(Archive& ar, const unsigned int /* version */)
+  {
+    ar & data::CreateNVP(weights, "weights");
+    ar & data::CreateNVP(lambda, "lambda");
+    ar & data::CreateNVP(beta, "beta");
+    ar & data::CreateNVP(rho, "rho");
+  }
 
  private:
   //! Locally-stored number of input units.