The notable victories achieved by the Protestants over the Roman clergy at the last two Diets opened the way wide to the spread of the Reformation. They also encouraged the szlachta to go still farther in their efforts to emancipate themselves from the power of the clergy. With ecclesiastical jurisdiction practically abolished, the szlachta began now to question the legitimacy of tithes. They were led to this by the insistence of the clergy that the tithes be paid, and by continuing to summon before their courts those who failed to do so and even the starostas who, in compliance with the law of the Diet of 1562-1563, refused to execute the verdicts of their courts. When, therefore, the Diet of 1565 assembled at Piotrków on January 18, the Chamber under the presidency of Nicholas Siennicki wanted to know the ground on which the szlachta was required to pay the tithes and the purposes for which the clergy were using them. And since the clergy was unwilling to share the burden of the country’s defense, the szlachta was disinclined to pay the tithes.[174] The Deputies complained also about the summons served by episcopal courts on the szlachta for non-payment of tithes and on the starostas for refusing to execute episcopal decrees; whereupon the king sanctioned a law making all such summons null and void.[175] This was the last blow administered to the effectiveness of ecclesiastical jurisdiction; and as a result of it the victory of the Protestants was complete. An idea of the relative strength and influence of Protestantism at this time may be gained from the composition of the Senate in the Diet of 1569, the number of Protestant parishes in the realm, and from a complaint of Peter Skarga, the greatest Jesuit preacher in Poland at the close of the 16th and the beginning of the 17th century. The total number of senatorial seats in the Diet of 1569 was 133. Of these 70 were occupied by Catholics, 15 of whom were bishops, 58 by Protestant dignitaries, 2 by Greek Orthodox senators, and 3 were vacant. Of the total number of senators the Protestants came close to having one-half, and, exclusive of the Catholic bishops, the Protestants outnumbered the Catholic temporal peers by three.[176] The number of Protestant parishes in Poland toward the close of the 16th century, according to Professor Henry Merczyng’s researches and calculations, was about 600, or one-sixth of the total number of Roman Catholic parishes in Poland including Lithuania. The same relative proportion existed between the Protestant and the Catholic szlachta of Poland at this time.[177] That this estimate of Professor Merczyng’s of Protestant strength in Poland at this time is very conservative can be seen from Peter Skarga’s complaint, made at the close of the 16th century, that two thousand Romanist churches had been converted into Protestant places of worship.[178]