Describe how a person of quality who also acts as gulliver's interpretes tells him about Struld brugs,the immortals

Gulliver was told that in the island of Luggnagg few people were born with a red circle on their foreheads, just above the left eyebrow.they were destined to be immortals, They were called struldbruggs. He was also told that this red spot changed colour with time and grew larger. It remains red from birth till the age of twelve, from twelve to twenty-five it changed to green, then it turned to deep blue and remained so till forty-five years of age, and lastly changes to black permanently. The size also becomes permanent once it is coal black in colour. These births are a matter of chance and are not specific to class or gender. Even the children of immortals are mortals like the majority, similarly, the mortals can have immortal children. The interpreter also shares the rarity of such births and tells that there were only eleven hundred immortals in the kingdom.