Spectrophotometrical investigation of NGC 3353.

Results of detailed spectrophotometric investigations of NGC 3353 are presented. Four separate condensations, the brightest of which is Mark 35, are studied. In the spectrum of Mark 35 the emission lines from Hα to H₁₂, He I λλ7065, 6678, 5876, 4922, 4472, 3820 and forbidden lines [O I] λλ6300/64, [O II] λ3727, [O III] λλ5007, 4959, 4363, [Ne III] λ3869, [N II] λλ6584/48, [S II] λλ6717/31, [S III] λ6310, [Ar III] λ7136 are detected. In the second central condensation, called "nucleus", emission lines are weaker and beginning with Hβ the absorption components appear which become stronger in the late members of Balmer lines. The forbidden lines in the nucleus are strong: [Ne III], [O III], [O II], [S II], [N II]. The relative intensities and equivalent widths of emission lines as well as the chemical composition of Mark 35 and "nucleus" are estimated. Both condensations according to their physical properties look like superassociations. It has been concluded that the source of excitation are young stars. NGC 3353 is probably a net of superassociations.