diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 312617c4e..5150f97ec 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -109,21 +109,4 @@ class ApplicationController < ActionController::Base
       end
     end
 
-    def track_activity(trackable)
-      if trackable.is_a? Comment
-        action = trackable.root? ? "debate_comment" : "comment_reply"
-        activity = current_user.activities.create! action: action, trackable: trackable
-        add_notifications_for activity
-      end
-    end
-
-    def add_notifications_for(activity)
-      case activity.action
-      when "debate_comment"
-        author = activity.trackable.debate.author
-      when "comment_reply"
-        author = activity.trackable.parent.author
-      end
-      author.notifications.create!(activity: activity) unless activity.made_by? author
-    end
 end
diff --git a/app/controllers/comments_controller.rb b/app/controllers/comments_controller.rb
index e05be448a..c30ddbaf2 100644
--- a/app/controllers/comments_controller.rb
+++ b/app/controllers/comments_controller.rb
@@ -9,7 +9,7 @@ class CommentsController < ApplicationController
   def create
     if @comment.save
       CommentNotifier.new(comment: @comment).process
-      track_activity @comment
+      add_notification @comment
     else
       render :new
     end
@@ -63,4 +63,13 @@ class CommentsController < ApplicationController
       ["1", true].include?(comment_params[:as_moderator]) && can?(:comment_as_moderator, @commentable)
     end
 
+    def add_notification(comment)
+      if comment.reply?
+        author = comment.parent.author
+      else
+        author = comment.commentable.author
+      end
+      author.notifications.create!(notifiable: comment) unless comment.made_by? author
+   end
+
 end
diff --git a/app/controllers/notifications_controller.rb b/app/controllers/notifications_controller.rb
index 199893bd7..8ecb16104 100644
--- a/app/controllers/notifications_controller.rb
+++ b/app/controllers/notifications_controller.rb
@@ -3,8 +3,7 @@ class NotificationsController < ApplicationController
   load_and_authorize_resource class: "User"
 
   def index
-    @notifications = current_user.notifications.unread.recent.for_render
-    @notifications.each { |notification| notification.mark_as_read! }
+    @notifications = current_user.notifications.recent.for_render
   end
 
 end
diff --git a/app/helpers/notifications_helper.rb b/app/helpers/notifications_helper.rb
index d0e7e71a9..45ef6422f 100644
--- a/app/helpers/notifications_helper.rb
+++ b/app/helpers/notifications_helper.rb
@@ -1,16 +1,15 @@
 module NotificationsHelper
 
   def notification_text_for(notification)
-    case notification.activity.action
-    when "debate_comment"
-     t("comments.notifications.commented_on_your_debate")
-    when "comment_reply"
-     t("comments.notifications.replied_to_your_comment")
+    if notification.notifiable.reply?
+      t("comments.notifications.replied_to_your_comment")
+    else
+      t("comments.notifications.commented_on_your_debate")
     end
   end
 
   def notifications_class_for(user)
-    user.notifications.unread.count > 0 ? "with_notifications" : "without_notifications"
+    user.notifications.count > 0 ? "with_notifications" : "without_notifications"
   end
 
 end
diff --git a/app/models/comment.rb b/app/models/comment.rb
index 3771af84a..44e16b729 100644
--- a/app/models/comment.rb
+++ b/app/models/comment.rb
@@ -90,6 +90,10 @@ class Comment < ActiveRecord::Base
     !root?
   end
 
+  def made_by?(user)
+    self.user == user
+  end
+
   def call_after_commented
     self.commentable.try(:after_commented)
   end
diff --git a/app/models/notification.rb b/app/models/notification.rb
index 0f387f61f..63f44dedc 100644
--- a/app/models/notification.rb
+++ b/app/models/notification.rb
@@ -1,16 +1,19 @@
 class Notification < ActiveRecord::Base
   belongs_to :user
-  belongs_to :activity
+  belongs_to :notifiable, polymorphic: true
 
-  scope :unread, -> { where(read: false) }
+  scope :unread, -> { all }
   scope :recent, -> { order(id: :desc) }
-  scope :for_render, -> { includes(activity: [:user, :trackable]) }
+  scope :for_render, -> { includes(notifiable: [:user]) }
+
+  def username
+    notifiable.user.username
+  end
 
   def timestamp
-    activity.trackable.created_at
+    notifiable.created_at
   end
 
   def mark_as_read!
-    update_attribute :read, true
   end
-end
+end
\ No newline at end of file
diff --git a/app/views/notifications/index.html.erb b/app/views/notifications/index.html.erb
index ab4351c50..0155f0521 100644
--- a/app/views/notifications/index.html.erb
+++ b/app/views/notifications/index.html.erb
@@ -3,8 +3,8 @@
     <% @notifications.each do |notification| %>
     <li>
       <time><%= l notification.timestamp, format: :datetime %></time>&nbsp;&bull;&nbsp;
-      <%= notification.activity.username %> <%= notification_text_for(notification) %> 
-      <%= link_to notification.activity.trackable.debate.title, notification.activity.trackable.debate %>
+      <%= notification.username %> <%= notification_text_for(notification) %>
+      <%= link_to notification.notifiable.commentable.title, notification.notifiable.commentable %>
     </li>
     <% end %>
   </ul>
diff --git a/db/migrate/20150928075646_create_activities.rb b/db/migrate/20150928075646_create_activities.rb
deleted file mode 100644
index 89b0edcbc..000000000
--- a/db/migrate/20150928075646_create_activities.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-class CreateActivities < ActiveRecord::Migration
-  def change
-    create_table :activities do |t|
-      t.belongs_to :user, index: true, foreign_key: true
-      t.string :action
-      t.belongs_to :trackable, polymorphic: true
-    end
-  end
-end
diff --git a/db/migrate/20160105170113_merge_activities_and_notifications.rb b/db/migrate/20160105170113_merge_activities_and_notifications.rb
new file mode 100644
index 000000000..fac5b213d
--- /dev/null
+++ b/db/migrate/20160105170113_merge_activities_and_notifications.rb
@@ -0,0 +1,10 @@
+class MergeActivitiesAndNotifications < ActiveRecord::Migration
+  def change
+    change_table :notifications do |t|
+      t.remove :read
+      t.remove :activity_id
+      t.references :notifiable, polymorphic: true
+    end
+  end
+
+end
diff --git a/db/schema.rb b/db/schema.rb
index cb1c5aa65..35aa4b68c 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20151215165824) do
+ActiveRecord::Schema.define(version: 20160105170113) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -205,14 +205,11 @@ ActiveRecord::Schema.define(version: 20151215165824) do
   add_index "moderators", ["user_id"], name: "index_moderators_on_user_id", using: :btree
 
   create_table "notifications", force: :cascade do |t|
-    t.integer  "user_id"
-    t.integer  "activity_id"
-    t.boolean  "read",        default: false
-    t.datetime "created_at",                  null: false
-    t.datetime "updated_at",                  null: false
+    t.integer "user_id"
+    t.integer "notifiable_id"
+    t.string  "notifiable_type"
   end
 
-  add_index "notifications", ["activity_id"], name: "index_notifications_on_activity_id", using: :btree
   add_index "notifications", ["user_id"], name: "index_notifications_on_user_id", using: :btree
 
   create_table "organizations", force: :cascade do |t|
@@ -407,7 +404,6 @@ ActiveRecord::Schema.define(version: 20151215165824) do
   add_index "votes", ["votable_id", "votable_type", "vote_scope"], name: "index_votes_on_votable_id_and_votable_type_and_vote_scope", using: :btree
   add_index "votes", ["voter_id", "voter_type", "vote_scope"], name: "index_votes_on_voter_id_and_voter_type_and_vote_scope", using: :btree
 
-  add_foreign_key "activities", "users"
   add_foreign_key "administrators", "users"
   add_foreign_key "annotations", "legislations"
   add_foreign_key "annotations", "users"
@@ -416,7 +412,6 @@ ActiveRecord::Schema.define(version: 20151215165824) do
   add_foreign_key "identities", "users"
   add_foreign_key "locks", "users"
   add_foreign_key "moderators", "users"
-  add_foreign_key "notifications", "activities"
   add_foreign_key "notifications", "users"
   add_foreign_key "organizations", "users"
 end
diff --git a/spec/factories.rb b/spec/factories.rb
index 8cdd3a3e4..d48aba942 100644
--- a/spec/factories.rb
+++ b/spec/factories.rb
@@ -291,9 +291,8 @@ FactoryGirl.define do
   end
 
   factory :notification do
-    association :user, factory: :user
-    association :activity, factory: :activity
-    read false
+    user
+    association :notifiable, factory: :comment
   end
 
 end
diff --git a/spec/helpers/notifications_helper_spec.rb b/spec/helpers/notifications_helper_spec.rb
index 120369bf4..dd5cd1b78 100644
--- a/spec/helpers/notifications_helper_spec.rb
+++ b/spec/helpers/notifications_helper_spec.rb
@@ -3,20 +3,21 @@ require 'rails_helper'
 describe NotificationsHelper do
 
   describe "#notification_text_for" do
-    let(:comment_activity) { create :activity, action: "debate_comment" }
-    let(:reply_activity) { create :activity, action: "comment_reply" }
+    let(:debate) { create :debate }
+    let(:debate_comment) { create :comment, commentable: debate }
+    let(:comment_reply)  { create :comment, commentable: debate, parent: debate_comment }
 
     context "when action was comment on a debate" do
-      it "returns 'commented_on_your_debate' locale text" do
-        notification = create :notification, activity: comment_activity
-        expect(notification_text_for(notification)).to eq t("comments.notifications.commented_on_your_debate")
+      it "returns correct text when someone comments on your debate" do
+        notification = create :notification, notifiable: debate_comment
+        expect(notification_text_for(notification)).to eq "commented on your debate"
       end
     end
 
     context "when action was comment on a debate" do
-      it "returns 'replied_to_your_comment' locale text" do
-        notification = create :notification, activity: reply_activity
-        expect(notification_text_for(notification)).to eq t("comments.notifications.replied_to_your_comment")
+      it "returns correct text when someone replies to your comment" do
+        notification = create :notification, notifiable: comment_reply
+        expect(notification_text_for(notification)).to eq "replied to your comment on"
       end
     end
   end
diff --git a/spec/models/comment_spec.rb b/spec/models/comment_spec.rb
index 11a02400a..684de6438 100644
--- a/spec/models/comment_spec.rb
+++ b/spec/models/comment_spec.rb
@@ -128,4 +128,19 @@ describe Comment do
       expect(Comment.not_as_admin_or_moderator.first).to eq(comment1)
     end
   end
+
+  describe "#made_by?" do
+    let(:author)  { create :user }
+    let(:comment) { create :comment, user: author }
+
+    it "returns true if comment was made by user" do
+      expect(comment.made_by?(author)).to be true
+    end
+
+    it "returns false if comment was not made by user" do
+      not_author = create :user
+      expect(comment.made_by?(not_author)).to be false
+    end
+  end
+
 end
diff --git a/spec/models/notification_spec.rb b/spec/models/notification_spec.rb
index 8d5e3dd97..d93dcf6f3 100644
--- a/spec/models/notification_spec.rb
+++ b/spec/models/notification_spec.rb
@@ -26,8 +26,8 @@ describe Notification do
   end
 
   describe "#for_render (scope)" do
-    it "returns notifications with including activity, user and trackable info" do
-      expect(Notification).to receive(:includes).with(activity: [:user, :trackable]).exactly(:once)
+    it "returns notifications including notifiable and user" do
+      expect(Notification).to receive(:includes).with(notifiable: [:user]).exactly(:once)
       Notification.for_render
     end
   end
@@ -35,8 +35,7 @@ describe Notification do
   describe "#timestamp" do
     it "returns the timestamp of the trackable object" do
       comment = create :comment
-      activity = create :activity, trackable: comment
-      notification = create :notification, activity: activity
+      notification = create :notification, notifiable: comment
 
       expect(notification.timestamp).to eq comment.created_at
     end
@@ -51,4 +50,13 @@ describe Notification do
       expect(notification.read).to be true
     end
   end
+
+  describe "#username" do
+    it "returns the username of the activity's author" do
+      comment = create :comment
+      notification = create :notification, notifiable: comment
+      expect(notification.username).to eq comment.author.username
+    end
+  end
+
 end