diff --git a/.gitignore b/.gitignore
index e63dffc..8699683 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,6 +5,7 @@
 *.egg-info/
 *.egg/
 .coverage
+coverage.xml
 .project
 .idea/
 .pydevproject
diff --git a/.travis.yml b/.travis.yml
index 175a66b..5601d0a 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,98 +10,98 @@ python:
   - "3.5"
   - "3.6"
 env:
-  - DJANGO="Django>=1.4,<1.5"
-  - DJANGO="Django>=1.5,<1.6"
-  - DJANGO="Django>=1.6,<1.7"
-  - DJANGO="Django>=1.7,<1.8"
-  - DJANGO="Django>=1.8,<1.9"
-  - DJANGO="Django>=1.9,<1.10"
-  - DJANGO="Django>=1.10,<1.11"
-  - DJANGO="Django>=1.11,<1.12"
-  - DJANGO="https://github.com/django/django/tarball/master"
+  - TOXENV="django14"
+  - TOXENV="django15"
+  - TOXENV="django16"
+  - TOXENV="django17"
+  - TOXENV="django18"
+  - TOXENV="django19"
+  - TOXENV="django110"
+  - TOXENV="django111"
+  - TOXENV="djangodev"
 
 matrix:
+  fast_finish: true
   exclude:
-  - python: "3.6"
-    env: DJANGO="Django>=1.4,<1.5"
-  - python: "3.6"
-    env: DJANGO="Django>=1.5,<1.6"
-  - python: "3.6"
-    env: DJANGO="Django>=1.6,<1.7"
-  - python: "3.6"
-    env: DJANGO="Django>=1.7,<1.8"
-  - python: "3.6"
-    env: DJANGO="Django>=1.8,<1.9"
-  - python: "3.6"
-    env: DJANGO="Django>=1.9,<1.10"
-  - python: "3.6"
-    env: DJANGO="Django>=1.10,<1.11"
+    - python: "3.6"
+      env: TOXENV="django14"
+    - python: "3.6"
+      env: TOXENV="django15"
+    - python: "3.6"
+      env: TOXENV="django16"
+    - python: "3.6"
+      env: TOXENV="django17"
+    - python: "3.6"
+      env: TOXENV="django18"
+    - python: "3.6"
+      env: TOXENV="django19"
+    - python: "3.6"
+      env: TOXENV="django110"
 
-  - python: "3.5"
-    env: DJANGO="Django>=1.4,<1.5"
-  - python: "3.5"
-    env: DJANGO="Django>=1.5,<1.6"
-  - python: "3.5"
-    env: DJANGO="Django>=1.6,<1.7"
-  - python: "3.5"
-    env: DJANGO="Django>=1.7,<1.8"
+    - python: "3.5"
+      env: TOXENV="django14"
+    - python: "3.5"
+      env: TOXENV="django15"
+    - python: "3.5"
+      env: TOXENV="django16"
+    - python: "3.5"
+      env: TOXENV="django17"
 
-  - python: "3.4"
-    env: DJANGO="Django>=1.4,<1.5"
-  - python: "3.4"
-    env: DJANGO="Django>=1.9,<1.10"
-  - python: "3.4"
-    env: DJANGO="Django>=1.10,<1.11"
-  - python: "3.4"
-    env: DJANGO="Django>=1.11,<1.12"
+    - python: "3.4"
+      env: TOXENV="django14"
+    - python: "3.4"
+      env: TOXENV="django19"
+    - python: "3.4"
+      env: TOXENV="django110"
+    - python: "3.4"
+      env: TOXENV="django111"
 
-  - python: "3.3"
-    env: DJANGO="Django>=1.4,<1.5"
-  - python: "3.3"
-    env: DJANGO="Django>=1.9,<1.10"
-  - python: "3.3"
-    env: DJANGO="Django>=1.10,<1.11"
-  - python: "3.3"
-    env: DJANGO="Django>=1.11,<1.12"
-  - python: "3.3"
-    env: DJANGO="https://github.com/django/django/tarball/master"
+    - python: "3.3"
+      env: TOXENV="django14"
+    - python: "3.3"
+      env: TOXENV="django19"
+    - python: "3.3"
+      env: TOXENV="django110"
+    - python: "3.3"
+      env: TOXENV="django111"
+    - python: "3.3"
+      env: TOXENV="djangodev"
 
-  - python: "3.2"
-    env: DJANGO="Django>=1.4,<1.5"
-  - python: "3.2"
-    env: DJANGO="Django>=1.9,<1.10"
-  - python: "3.2"
-    env: DJANGO="Django>=1.10,<1.11"
-  - python: "3.2"
-    env: DJANGO="Django>=1.11,<1.12"
-  - python: "3.2"
-    env: DJANGO="https://github.com/django/django/tarball/master"
+    - python: "3.2"
+      env: TOXENV="django14"
+    - python: "3.2"
+      env: TOXENV="django19"
+    - python: "3.2"
+      env: TOXENV="django110"
+    - python: "3.2"
+      env: TOXENV="django111"
+    - python: "3.2"
+      env: TOXENV="djangodev"
+
+    - python: "2.6"
+      env: TOXENV="django17"
+    - python: "2.6"
+      env: TOXENV="django18"
+    - python: "2.6"
+      env: TOXENV="django19"
+    - python: "2.6"
+      env: TOXENV="django110"
+    - python: "2.6"
+      env: TOXENV="django111"
+    - python: "2.6"
+      env: TOXENV="djangodev"
 
-  - python: "2.6"
-    env: DJANGO="Django>=1.7,<1.8"
-  - python: "2.6"
-    env: DJANGO="Django>=1.8,<1.9"
-  - python: "2.6"
-    env: DJANGO="Django>=1.9,<1.10"
-  - python: "2.6"
-    env: DJANGO="Django>=1.10,<1.11"
-  - python: "2.6"
-    env: DJANGO="Django>=1.11,<1.12"
-  - python: "2.6"
-    env: DJANGO="https://github.com/django/django/tarball/master"
   allow_failures:
-    - env: DJANGO="https://github.com/django/django/tarball/master"
+    - env: TOXENV="djangodev"
 
 before_install:
-- pip install codecov
-
-install:
-  - pip install -q $DJANGO coverage==3.6
+- pip install codecov coverage==3.6 tox
 
 script:
-  - coverage run --source=polymorphic runtests.py
+  - tox
 
 after_success:
+- coverage xml -i
 - codecov
 
 branches:
diff --git a/README.rst b/README.rst
index 4c769cf..f72b011 100644
--- a/README.rst
+++ b/README.rst
@@ -1,4 +1,4 @@
-.. image::  https://travis-ci.org/django-polymorphic/django-polymorphic.png?branch=master
+.. image::  https://travis-ci.org/django-polymorphic/django-polymorphic.svg?branch=master
     :target: http://travis-ci.org/django-polymorphic/django-polymorphic
 .. image:: https://img.shields.io/pypi/v/django-polymorphic.svg
     :target: https://pypi.python.org/pypi/django-polymorphic/
diff --git a/polymorphic/query.py b/polymorphic/query.py
index 0d716ff..209d7a2 100644
--- a/polymorphic/query.py
+++ b/polymorphic/query.py
@@ -39,6 +39,8 @@ def _polymorhic_iterator(queryset, base_iter):
         base_result_objects = []
         reached_end = False
 
+        # Make sure the base iterator is read in chunks instead of
+        # reading it completely, in case our caller read only a few objects.
         for i in range(Polymorphic_QuerySet_objects_per_request):
             try:
                 o = next(base_iter)
@@ -47,17 +49,17 @@ def _polymorhic_iterator(queryset, base_iter):
                 reached_end = True
                 break
 
-        real_results = queryset._get_real_instances(base_result_objects)
+            real_results = queryset._get_real_instances(base_result_objects)
 
-        for o in real_results:
-            yield o
+            for o in real_results:
+                yield o
 
-        if reached_end:
-            return
+            if reached_end:
+                return
 
 
 if django.VERSION >= (1, 9):
-
+    # We ignore this on django < 1.9, as ModelIterable didn't yet exist.
     from django.db.models.query import ModelIterable
 
     class PolymorphicModelIterable(ModelIterable):
@@ -115,8 +117,9 @@ class PolymorphicQuerySet(QuerySet):
     def __init__(self, *args, **kwargs):
         super(PolymorphicQuerySet, self).__init__(*args, **kwargs)
         if django.VERSION >= (1, 9):
+            # On django < 1.9 we override the iterator() method instead
             self._iterable_class = PolymorphicModelIterable
-        # init our queryset object member variables
+
         self.polymorphic_disabled = False
         # A parallel structure to django.db.models.query.Query.deferred_loading,
         # which we maintain with the untranslated field names passed to
@@ -460,8 +463,22 @@ class PolymorphicQuerySet(QuerySet):
         return resultlist
 
     if django.VERSION < (1, 9):
-        # Before Django 1.9 ModelIterable functionality was implemented in `iterator` method
+        # On django 1.9+, we can define self._iterator_class instead of iterator()
         def iterator(self):
+            """
+            This function is used by Django 1.8 and earlier for all object retrieval.
+            By overriding it, we modify the objects that this queryset returns
+            when it is evaluated (or its get method or other object-returning methods are called).
+
+            Here we do the same as::
+
+                base_result_objects = list(super(PolymorphicQuerySet, self).iterator())
+                real_results = self._get_real_instances(base_result_objects)
+                for o in real_results: yield o
+
+            but it requests the objects in chunks from the database,
+            with Polymorphic_QuerySet_objects_per_request per chunk
+            """
             base_iter = super(PolymorphicQuerySet, self).iterator()
 
             # disabled => work just like a normal queryset
diff --git a/tox.ini b/tox.ini
index ee02b1b..cff1ea7 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,14 +5,13 @@ envlist=
     py32-django{15,16,17,18},
     py33-django{15,16,17,18},
     py34-django{15,16,17,18,19,110,111},
-    py35-django{18,19,110,111}
-    py35-django{18,19,110,111},
-    py36-django{111},
-    # py33-django-dev,
+    py35-django{18,19,110,111,dev},
+    py36-django{111,dev},
     docs,
 
 [testenv]
 deps =
+    coverage == 3.6
     django14: Django >= 1.4, < 1.5
     django15: Django >= 1.5, < 1.6
     django16: Django >= 1.6, < 1.7
@@ -21,9 +20,9 @@ deps =
     django19: Django >= 1.9, < 1.10
     django110: Django >= 1.10, < 1.11
     django111: Django >= 1.11, < 1.12
-    django-dev: https://github.com/django/django/tarball/master
+    djangodev: https://github.com/django/django/tarball/master
 commands=
-    python runtests.py
+    coverage run --source polymorphic runtests.py
 
 [testenv:docs]
 deps=Sphinx