I  honestly don't know if amoebas have blood flow. My thoughts would be no, but I don't want to state it as fact. I do know that I have long heard the saying that "blood is thicker than water" meaning that people will stick by blood relatives before they will stick by anyone else. Well, it turns out that even the simplest creature, the amoeba, will turn to family in times of trouble and will sacrifice themselves for other family members! So assuming that a single-cell organism doesn't have a circulatory system (where would it have room for it?), then I think the saying needs to be changed..."Family Ties are Stronger than Friendships"...hmmm, not quite as catchy is it? Feel free to make your own suggestions!