you can although it is more difficult but it really depends on the supervisor rather than the university.
because i also applied through that way to 2 supervisors within the same uni: one said ok without masters, another one said no..
but again it also depends what you get with your bachelor. often you need to be pretty good if you are to compare yourself with other applicant with masters.

please remember that some supervisors will challenge you and may discourage you but you have to show yourself to them as being quite determined...

i'd recommend you look through the project you are interested in first, contact supervisor -- getting the paper work done with the uni comes last usually...
if there is good enough reasons, uni should accept doctoral student without masters.