The defendant was convicted of armed robbery after a trial held pursuant to the provisions of G. L. c. 278, Sections 33A-33G. Although the defendant acted as his own attorney, the court afforded him the continual presence and assistance of a member of the Massachusetts Defenders Committee during the trial. The one assignment of error asserts that the trial judge erred in failing to charge the jury "sua sponte" on the "law of circumstantial evidence." As no exception was taken to any part of the charge, the assignment of error brings nothing to this court for review. Commonwealth v. McCauley, 355 Mass. 554 , 558 (1969). Commonwealth v. Lauria, 359 Mass. 168 , 172 (1971). The defendant asks us to exercise the power referred to in Commonwealth v. Conroy, 333 Mass. 751 , 756-757 (1956), and Commonwealth v. Freeman, 352 Mass. 556 , 564
(1967). Our examination of the transcript of the trial, including the judge's charge, does not reveal any likelihood of a miscarriage of justice.