From the fifteenth century onwards the Vice-Chancellor takes the place of the Chancellor as the centre of University life; as the Chancellor's representative, he is nominated every year by letters from him, though the appointment is in theory approved by the vote of Convocation. The nomination of a Vice-Chancellor is for a year, but renomination is allowed; as a matter of fact, the Chancellor's choice is limited by custom in two ways; no Vice-Chancellor is reappointed more than three times, i.e. the tenure of the office is limited to four years, and the nomination is always offered to the senior head of a house who has not held the position already; if any head has declined the office when offered to him on a previous occasion, he is treated as if he had actually held it. The Vice-Chancellor has all the powers and duties of the Chancellor in the latter's absence; but in the rare cases when the Chancellor visits Oxford, his deputy sinks for the time into the position of an ordinary head of a college. [Sidenote: The Control of Examinations.] The only duties of the Vice-Chancellor that need be here mentioned are his authority and control over examinations and over degrees, duties which are of course connected. Any departure from the ordinary course of proceeding needs his approval: e.g. (to take a constantly recurring case) he alone can give permission to examine an undergraduate out of his turn, when any one has failed to present himself at the right time for viva voce. Now that all Oxford arrangements for examinations have developed into a cast-iron system, the appeal, except in matters of detail, to the Vice-Chancellor is rare; but it was not always so; his control was at one time a very real and important matter. In the case of the famous Dr. Fell, Dean of Christ Church, Antony Wood notes 'that he did frequent examinations for degrees, hold the examiners up to it, and if they would or could not do their duty, he would do it himself, to the pulling down of many'. It is no wonder that men said of him:-- I do not like thee, Dr. Fell, The reason why I cannot tell. He was equally careful of the decencies and proprieties of the degree ceremony; 'his first care (as Vice-Chancellor) was to make all degrees go in caps, and in public assemblies to appear in hoods. He also reduced the caps and gowns worn by all degrees to their former size and make, and ordered all cap-makers and tailors to make them so.'