You seem to be unaware of something:There was no country Poland in the time period you refer to!In the late 18th century, Poland was partitioned three times -- in 1772, 1793, and 1795.The partitions divided Poland among Russia (which got by far the lion's share), the German state of Prussia -- (like the U.S., Germany has always been made up of states) -- and Austria.Poland thereupon disappeard from the map as an independent nation for almost 125 years, until the western Allies re-established an independent Poland following World War I.In the time period you refer to, all those towns were located in the GERMAN state of PRUSSIA!
Towns a, c, and d were located in what was until 1918 the Prussian province of Posen (capital: city of Posen; in Polish: Poznan), and town b was located in what was until 1918 the Prussian province of West Prussia (capital: Danzig; now known by the Polish name Gdansk).
In the time period you refer to: (a) Kcynia was known by the German name Exin and was located in the District (in German: Kreis) of Schubin (the German name for Szubin) in the Prussian province of Posen; (b) Tupadly was known by the German name Tupadel and was located in the District (Kreis) of Putzig (the German name for Puck) in the Prussian province of West Prussia; (c) Bydgoszcz was known by the German name Bromberg and was the seat of the District (Kreis) of the same name in the Prussian province of Posen; and (d) Lekno was also known as Lekno in German and was located in the District (Kreis) of Wongrowitz (the German name for Wagrowiec) in the Prussian province of Posen.
(A Kreis, abbreviated Kr., is roughly equivalent to a county in a U.S. state.)
The places as you've written them here in your posting would be correct if you were referring to 1920 or later.In the time period you refer to, the correct designations would be:
(a) Exin, Kr. Schubin, Posen, Prussia, Germany (b) Tupadel, Kr. Putzig, West Prussia, Prussia, Germany (c) Bromberg, Posen, Prussia, Germany (d) Lekno, Kr. Wongrowitz, Posen, Prussia, Germany
(Even though Germany did not become a politically unified country until 1871, for genealogical purposes, Germany should be included in the place designations.)
Here is the link to a map of Germany as it was from its unification under Bismarck in 1871 until 1918.You will see Germany's states, including Prussia (in German: Preussen; pronounced: PROY-s'n), Germany's largest state by far, and its provinces.If you look to the east, you will see the Prussian provinces of Posen and West Prussia, mentioned above.You will also note how vast Prussia was.It stretched from East Prussia in the northeast, all the way to and including the Rhineland in the west.That's a distance of close to 900 miles or 1500 km!Berlin was Prussia's state capital, and from 1871, Germany's national capital as well: