As Jack experiments with hunting the pigs, he troubleshoots his difficulties along the way to discover the best possible way for catching and killing a pig. One of his issues is that he cannot lodge the spear into the pig; the spear keeps sliding out.
When Jack meets up with Ralph in chapter three, Ralph is incensed that nobody is helping him build the shelters, fully insinuating that if Jack cannot kill a pig, then the least he could do is to help out around camp. Instead of acknowledging Ralph's frustration, Jack makes excuses for his inability to kill a pig:
"But I shall [kill a pig]! Next time! I've got to get a barb on this spear! We wounded a pig and the spear fell out. If we could only make barbs--" (51).
Jack's quest to improve his hunting technology reveals his ability to think critically and improvise. He will devise a barbed spear, and the next hunt will prove successful.