In1861itseemedinevitablethattheSouthernstateswouldbreakawayfromtheUnion.
Thecontrolsofmostmodernairplanescanbeoperatedeithermanuallyorautomatically.
TheeconomyofDallas,Texas,isstronganddiversified.
Eyespots,themostrudimentaryeyes,arefoundinprotozoan原生动物flagellates鞭毛虫,flatworms扁形虫,andsegmentedworms片段蠕虫.