21.   A complex weather pattern will evolve over the East on Tuesday, bringing snow to portions of the interior Northeast later Tuesday and Tuesday night.

22.   A genetic tendency that evolved over many centuries by which red blood cells are deformed into sickle shapes reduces their ability to metabolize nutrients.

23.   Actually, Forbes added, the lack of mementos shows how the festival here has evolved over its dozen years.

24.   Affirmative action also has changed state hiring practices, evolving over decades into a series of laws directing officials to recruit and hire women and minorities.

25.   After seeing a dozen of these running-mate decisions evolve over the years, you learn to put conditional words in all your sentences.

26.   But as the story has evolved over the years on the big screen, things have heated up.

27.   But in the end, these changes are only cosmetic, just barely concealing a band that has hardly evolved over its career.

28.   But like the XFL, the upstart professional football league, the success of digital books on the Web will depend on how the concept evolves over time.

29.   But in the short term, that process is likely to be slowed by a maze of contradictory regulation that has evolved over the years.

30.   But technologists, economists and futurists say that some questions are worth asking when thinking about how the Internet economy might evolve over the next few years.