diff --git a/README.md b/README.md
index efbfb44..07c257d 100644
--- a/README.md
+++ b/README.md
@@ -250,3 +250,18 @@ It would be fun to see if the Treeview widget could handle all the stars
 and planets...  12,300 planets, 1,948 stars, it should be able to handle
 it?
 
+
+Mon Apr 15 15:48:51 PDT 2024
+
+Pop growth on homeworlds only: we want the populations that are on a
+planet where that planet is in the home stellar system of the species of
+the population.
+
+planets.star = populations.homestar
+
+What if in the populations table instead of the species column there is a
+home system column?  We can get the species name from the homestar name
+as needed?
+
+Is there a good reason not to have the species name with the pops?  Extra
+space used I guess, maybe?  pop.homestar.name + 'ians'
diff --git a/data.py b/data.py
index aefc348..5f7e171 100644
--- a/data.py
+++ b/data.py
@@ -62,10 +62,22 @@ TABLES = [
         species TEXT,
         pop INTEGER,
         planet INTEGER,
+        vessel INTEGER,
+        station INTEGER,
         FOREIGN KEY(planet) REFERENCES planets(id)
-    )''',
+        check (
+            ( case when planet  is null then 0 else 1 end
+            + case when vessel  is null then 0 else 1 end
+            + case when station is null then 0 else 1 end
+            ) = 1
+        )
+    )
+    ''',
 ]
 
+# Apparently this clause should constrain a pop to be
+# in only one location at a time.
+
 
 def initialize_db_tables(filename):
     conn = open_db(filename)
diff --git a/game.sqlite b/game.sqlite
index 85b246d..baf6bb0 100644
Binary files a/game.sqlite and b/game.sqlite differ
diff --git a/population.py b/population.py
index 2eea1fc..391a95f 100644
--- a/population.py
+++ b/population.py
@@ -52,7 +52,7 @@ def init_db(conn):
             'insert into populations(species, pop, planet) values (?, ?, ?)',
             (people_name, INITIAL_POP, planet_id),
         )
-        print(planet_id, bio, industrial_capacity)
+        # print(planet_id, bio, industrial_capacity)
     c.close()
     conn.commit()
 
@@ -61,8 +61,8 @@ def get_name_of_planets_star(db_cursor, planet_id):
     # My first ever JOIN statement!  Squeeeee!
     db_cursor.execute(
         '''\
-        select stars.name from stars
-        join planets
+        select stars.name from
+        stars join planets
         on stars.id = planets.star
         and planets.id = ?
         ''',