Fishing is the most important industry. Jolo is the center for most of the pearling fleet. Sitanki, Omapui, Tumindao, Balimbing, Landubas, Laja, and Siasi are other important fishing centers. The sea turtle, fish of all kinds, and the trepang are caught. Beautiful trays and combs and other articles are made from the back of the sea turtle, and the fish and trepang are cured and exported. The Sulu Archipelago, especially Jolo, the capital and principal port, trades with Zamboanga, Borneo, and Singapore. Chinese merchants traded with Sulu long before the arrival of Legaspi in the Philippines. When Manila and Cebu were yet small settlements, Jolo was already a city, the most important in the Philippines. [Introduction of Mohammedanism] Mohammedanism was introduced and firmly established in the Archipelago by three men--Makdum, Raja Baginda, and Abu Bakr. Makdum was a noted Arabian scholar who, after introducing Mohammedanism into Malacca, visited almost every island of the Sulu Archipelago toward the end of the fourteenth century and made numerous converts especially in Bevansa and Tapul. Raja Baginda, soon after the arrival of Makdum, came by way of Zamboanga and Basilan. He was of princely rank and is believed to have come accompanied by ministers of state. He settled in Bevansa and became the supreme ruler of Sulu. Abu Bakr, who seemed to have been quite a learned man, arrived in Bevansa about the middle of the fifteenth century. Here, he lived with Raja Baginda, teaching the people the Mohammedan religion. He later married Parasimuli, the daughter of Raja Baginda, and succeeded his father-in-law as sultan. The reign of Abu Bakr (1450-1480) was noteworthy not only because of the firm establishment of Mohammedanism, but also because of the governmental reforms then effected. Abu Bakr reorganized the government of Sulu, dividing it into five main administrative districts, each under a Panglima. He promulgated a new code of laws which became the guide for all officials of the state. During his reign, Sulu's power was felt not only in Mindanao and the Visayas, but even in Luzon. The administration of Governor-General Sande (1575-80) was the beginning of a continuous state of warfare between Spain and Sulu which lasted to within two decades before the end of the Spanish rule. Sande wanted to reduce Sulu to a subject state, impose tribute on its people, secure for the Spaniards the trade of the Archipelago, and convert the inhabitants to Catholicism. To attain these ends, he sent Captain Rodriguez de Figueroa to Sulu with a large army. This expedition, however, accomplished nothing beyond the arousing of the Sulus to hostility and the inception of numerous Moro raids on the Visayas and Luzon. [The Sultan and His Present Position]