Filling of casual vacancy.

When any vacancy occurs in the office of a member (other than an ex-officio member) of any authority or other body of the University before the expiry of the term of office of such member, the vacancy shall be filled up, as soon as conveniently may be, by appointment or co-option, as the case may be, of a member who shall hold office so long only as the member in whose place he has been appointed or co-opted would have held it, if the vacancy had not occured.