On this appeal which is here under the provisions of G. L. c. 278, Sections 33A-33G, the defendant assigns as error joinder for trial of separate offences in two counts of one indictment. Each count alleges an unlawful sale of heroin, which sales allegedly occurred nine days apart. The judge did not abuse his discretion in the denial of the pre-trial motion for severance. The offences were kindred and liable to punishment of the same general character. See Commonwealth v. Iannello, 344 Mass. 723 , 727-728; Commonwealth v. Blow, ante, 196, 200. The defendant complains also of the introduction of evidence of previous convictions which when offered by the Commonwealth was not objected to. Commonwealth v. Nunes, 351 Mass. 401 , 405. Evidence of prior convictions of the defendant was properly admitted. Commonwealth v. Ladetto, 353 Mass. 746 . Subilosky v. Commonwealth,
358 Mass. 390 , 395-396. There was no error in refusing the defendant the opportunity to explain his prior convictions. Commonwealth v. Callahan, 358 Mass. 808 .