Jamaica's Usain Bolt remains on track for a World Championships sprint double after easing into the 200m semi-finals in Berlin's Olympic Stadium.Bolt, fresh from winning the 100m, won his second-round heat in 20.42 seconds.Britain's Marlon Devonish and Ireland's Paul Hession also qualified after Tyson Gay pulled out with a groin injury.In the 400m, defending champion Jeremy Wariner and Olympic champion Lashawn Merritt sauntered into the semi-finals by comfortably winning their heats.Gay's withdrawal from the 200m before the first round had already increased Bolt's chance of repeating his Beijing double, with the semi-finals scheduled for Wednesday at 1825 BST and the final on Thursday.Bolt looked tired in his morning heat and, despite cruising through the first 100m, the 22-year-old was forced to up his pace to ensure he qualified first in a time of in 20.70.But he seemed far more relaxed in the second round and cruised to victory after a few hours' sleep in between races."I think the 100m took a lot more out of me than it did in Beijing," said Bolt. "I wasn't in the best of shape, like I was in Beijing, but a good night's sleep should make sure I'm OK."I got three hours sleep after my morning heat and that was enough for me."Devonish, Britain's only representative after the withdrawals of Dwain Chambers and trials winner Toby Sandeman, won his morning heat before finishing third in his second-round run in a time of 20.66."I didn't execute the turn as well as I would have liked to so put more pressure on myself," the Coventry Godiva athlete told BBC Sport."I have to make sure I execute in the semi-finals and I should be fine. I want to get into the final and then let loose and see what happens."Hession finished second in his morning heat and third in his round-two run with a time of 20.48.Shawn Crawford, the 2004 Olympic gold medallist and 2008 Olympic silver medallist, looked in top form as he clocked 20.37.Jamaica's Steve Mullings was the fastest qualifier in 20.23, while 19-year-old Alonso Edward from Panama impressed in winning his heat in 20.33.Olympic champion Ezekiel Kemboi of Kenya broke clear in a frantic last lap to clinch the men's 3,000 metres steeplechase gold medal.Richard Kipkemboi Mateelong took silver with Frenchman Bouabdellah Tahri preventing a Kenyan clean sweep by finishing strongly and pipping Paul Koech on the line for bronze.Morocco's Jamel Chatbi withdrew from the final after testing positive in a doping test after the heats.Olympic bronze medallist Sanya Richards ran the fastest women's 400m of the year to win gold in 49 seconds.Fellow American Kerron Clement retained his men's 400m hurdles crown with a world best for the year of 47.91 seconds.The Olympic silver medallist beat Puerto Rico's Javier Culson who clocked 48.09, while 2005 world champion Bershawn Jackson was third in 48.23.Defending 400m champion Wariner, who was shocked by Merritt in Beijing last summer, progressed in 45.54 and Merritt impressed with a run of 45.23."It was a great race, I'm feeling good," Merritt told BBC Sport. "It's the semis tomorrow so I'll come out and step it up a notch."Last year was a good year and I plan on coming out on top again."Training's been going well and I had some good races. My times weren't amazing but they didn't need to be. I'm here, I'm ready and now I'll step it up."Source: BBC