Simplify the following text for a Grade 13 native English-speaking person.
Original: The peculiarities of the Greek system are further evidenced by the colonies that they set up throughout the Mediterranean Sea , which , though they might count a certain Greek polis as their ` mother ' ( and remain sympathetic to her ) , were completely independent of the founding city .
Simplified: The colonies they set up throughout the Mediterranean , though they counted a Greek polis as their ` mother ' ( and remain sympathetic to her ) , were completely independent of the founding city .